"Hasta los portales!" An enormous glass of frothy, murky, purple something is unceremoniously plonked on the checked tablecloth in front of me. I grip the drink with both hands, raise it silently in a toast – or a plea – and, as is the custom here in the Peruvian Andes, chug all the way down to a line marked halfway across the cup.

The flavours that hit my throat are… unusual. There's a musty yeastiness, followed by sweetness with hints of spice. Intrigued, I go for a second sip. It's refreshing and moreish, cool but not cold, and fizzes ever-so-gently against my tongue.

This is chicha de guiñapo, brewed and drunk in vast quantities in picanterías, the traditional family-run restaurants found throughout the Andes of Peru. Made with only a germinated purple corn (guiñapo) that's unique to the Arequipa region and some sugar, chicha is similar to beer, with an ABV of roughly 2-3%. The result is a rich, complex flavour that develops during an ancient fermentation process that takes place in giant earthenware tubs known as chomba, with the concho, or 'mother' bacteria that's used to ferment subsequent batches of the drink. And thanks to that bacteria, it's even considered to be good for you.

"The preparation of chicha hasn't changed for hundreds of years," Mónica Huerta Alpaca tells me, through translation. "It's rooted in Incan tradition, and having a good chicha is the hallmark of a good picantería."

Alpaca's happens to be one of the best, and she has the honoured position of being head of the Picantera Society of Arequipa. Picanteras are the Andina – Andean – women who run the picanterías in their homes, and dedicate their lives to serving food to their communities. Her chicha is famous, found at her picantería La Nueva Palomino under the clear light and deep blue skies of the Andes. We're just outside the centre of Arequipa, the colonial-era capital city of the Andean region, which sits at 2,335m above sea level. The mountains loom large in the distance – silent, immovable sentinels standing guard over an ancient society that serve as a constant, awe-inspiring reminder of where I am.

Alpaca talks me through the lengthy brewing process, which has been passed down for generations. She shows me how the liquid gets strained through nets made of jute, a material that's similar to hemp, using an 'uaua' movement, the same way you'd gently rock a baby to sleep.

This purple liquid holds a huge amount of tradition and ritual. It's unsurprising, given that chicha and picanterías go hand in hand; picanterías were originally chicharias, modest stalls serving drinks that evolved into sit-down restaurants more than 200 years ago, when the ladies who ran them started serving food to soak up all the booze.

But there's another reason why a good chicha means a good picantería. It can be boiled down to a thick liquid used in cooking to impart an incredible depth of flavour that's extremely hard – if not impossible – to replicate. The logic follows that when a picantería has a good chicha, you know it'll have a great picante, or stew.

I can personally vouch for the stew at La Nueva Palomino. It's Sunday morning, which means pork adobo is on the menu. The dish is a spicy, hangover-defeating, mouth-coating explosion of flavour – although that may be down to the deceptively hot rocoto pepper I accidentally eat in one go.

Once I've recovered, the picantera, who still wears a traditional outfit complete with hat, shows me the process of making golden ocopa sauce, which gets daubed over potatoes and other tubers. In it are huacatay (Peruvian black mint); sun-dried amarillo chilies; crackers; soft, creamy queso fresco, which is similar to feta; garlic; and peanuts. These ingredients are ground together using a batàn, a bit like a giant pestle and mortar, until they become smooth.

Potatoes at the market in the Peruvian Andes

Potatoes at the market in Arequipa

An elderly andina starts to mix everything together, her hands blurring as she picks up speed – I'm told the process is so finely honed that using a batàn is more efficient than using a blender. The ancient batàn's surface is as worn as the andina's face is lined; both have weathered a lifetime of experience. Alpaca doesn't know how old her family's stone is – research is being done to find out.

These batàns, used to make several sauces and picantes, are found in every picantería, and each one is unique. They are guarded so carefully that the batàn is hidden before service every day for fear that it will be stolen, although this is now more based on superstition than fact.

Everything around me, from the utensils themselves to the dishes being served, is shrouded in tradition. It rapidly becomes clear that to describe picanterías merely as restaurants is to do them an injustice. They are places of cultural exchange; they host social gatherings, political protests and live music; they are keeping the culture of the Andes alive, and the food they cook serves as a gateway to the region's past. The humble yet utterly delicious cuisine is born out of a local larder that's astonishingly varied.

Even in Peru, a country celebrated for its biodiversity, the Andes remain mysterious. The mountain range is vast, spanning seven different South American countries. Peru alone has 11 different Andina regions, each with their own influences – both ancient and modern – geographies and cultural identities, many of which resisted the changes brought by the Spanish Conquest, but are now sadly being forgotten. Arequipa, both a city and a region, is considered to be the gastronomic heartland.

Everything around me, from the utensils to the dishes, is shrouded in tradition.

It's worlds away from anywhere I've ever visited before, so I'm thankful for the knowledge of my guide, Martin Morales. Morales is the restaurateur at the helm of the Ceviche Family, a group of six restaurants: Ceviche Soho and Ceviche Old St, which revolve around the dishes of the capital city of Lima and coastal Peru; Andina in Shoreditch, Casita Andina, and now Andina and Andina Bakery in Notting Hill, which celebrate the cooking of the Andean region.

Thanks to Morales and others, Peruvian dishes and ingredients have slowly trickled onto our plates here in London, but many of these are inspired by the coast – there's a good chance ceviche is the dish you'll think of first. Andina cooking, on the other hand, is something most of us won't be familiar with, especially given that the cuisine is so ancient and on the verge of being forgotten that it remains relatively unknown, even in Lima.

"There's been a lack of knowledge, insight and passion," says Morales. "The high Andes are so remarkable that you have to travel there regularly to really get under the skin of the food culture, to study the ingredients and dishes and research the techniques." Morales's grandmother was an Andina picantera, and he grew up entrenched in Andean culture, which has led to his vision for sharing it with diners in London.

His passion for the ingredients is palpable as we explore the market in Arequipa. He takes me from stall to stall, sampling chicharrón, roast pork belly; caldo de gallina, chicken soup; the tiniest, sweetest bananas; tumbo, a type of elongated passion fruit; golden lucuma fruits, which you'll find painted on ancient Peruvian ceramics. And I see potatoes in their hundreds in all kinds of colours: shades of red, purple and yellow, and the powdery, white, freeze-dried (and funky-tasting) potato known as chuño blanco.

The cacophony of sounds, sights and smells is mesmerising. I take a wrong turn and end up in an underground room wreathed in smoke, where fortune tellers divine people's futures using coca leaves, which can also be brewed into a tea used to treat altitude sickness

"I've been travelling to the Andes since I was four years old," Morales tells me over freshly made juice from a market stall. "In the past few years my team and I have made 12 trips to the high Andes including Huancayo, Arequipa, Cajamarca, Puno, Cusco and Ayacucho. We want to bring these incredible stories back to London."

"We want to bring these incredible stories back to London"

But there's another reason why this is so important: preserving the past. With migration to the cities and people opting for education over such a hard way of life, two generations of picanteras and picanteros are missing, and the traditional recipes are being lost. Throw into the mix that most Peruvians who want to become chefs go to Lima to study European cooking, and it's unsurprising that Andina cuisine has suffered.

At Los Robles restaurant in Hotel Libertador, Arequipa, we find Eduardo Sernaqué, a modern picantero. His knowledge of traditional Andina dishes is second to none, and he's working hard to rediscover the traditional recipes.

In his elegant dining room, I eat potatoes drizzled with ocopa sauce; choclo con queso, Eduardo's take on the popular street food that uses Peru's pale, creamy yellow giant corn; cabrilla, a Peruvian rock sea bass with pumpkin; llama ossobuco and pesque de quinoa, which is a bit like an indulgent risotto that uses the nutty curlicues of quinoa grain; and much, much more.

The dishes of the Andes

Torrejas de Sachaca

The Sachaca district is known for its carrot fritters (pictured above), and the ones at picantería La Lucila are some of the best. They’re light and crunchy, served with a rocoto pepper sauce.

Sango

Sango was the main side dish in the Andes before rice was introduced. It’s made with wheat cooked with sugar cane, cinnamon, raisins and peanuts, and is often served alongside a meaty stew to soak up the juices.

Anticuchos

These cow heart kebabs are one of Peru’s best-known dishes, and you’ll find them being cooked at roadsides all around the country. 

Pachamanca

This ancient technique involves cooking meat underground, under large heated stones and banana leaves. Not one to try at home, then. 

Choclo con queso

Another popular street food snack, you can buy enormous cobs of the pale yellow giant corn native to Peru with creamy queso fresco just about anywhere. Added chili optional.

It's all undeniably delicious, but what strikes me most is that it's mainly the presentation that differs so much to the dishes that you eat in the picanterías. The plates are dressed so elegantly they'd easily fit in at a fine-dining restaurant in London. They taste equally good, too – but then they always did, even when I was eating them at the roadside and at market stalls.

The biggest difference comes in the surroundings. At La Lucila, a picantería in Arequipa's Sachaca district that's more than 100 years old, I sit in a kitchen with whitewashed adobo walls, where there's no electricity or gas, only running water. It's as rustic as you could possibly get. I eat ocopa sauce and pork adobo as guinea pigs squeak and skitter around on the kitchen floor.

Guinea pig is a traditional meat found all over the Andes. The little creatures are kept in the kitchens, free to run around – you could call them free range – before being used in a variety of dishes. Elsewhere, at a food market, I eat cuy (guinea pig) al palo, stuffed with Peruvian herbs and roasted over coals on a spit. The skin is crispy and addictive, like crackling, and the flesh is juicy. Even now, a few months later, I'm drooling. Those cute furry things are really damned tasty.

As I'm leaving a few days later, I feel I've barely scratched the surface. "Every time my chefs and I come back, we discover a new technique, grain, fruit, drink or dish," says Morales. "It's so important to us that we represent these flavours and stories authentically and with respect." 

I feel daunted by his mission. Later this month, Morales is opening another Andina and Andina Bakery, inspired by the research of this trip. For me, his main challenge will be to convey the Andean spirit to the mouths and hearts of trend-hungry Londoners.

Having travelled with his team of chefs for a week, I'm bowled over by their dedication and knowledge: "The way I see it, the flavours need to travel from your tongue to the thicker membrane of your heart," the Ceviche Family's executive chef Vitelio Reyes tells me. "I do that by making sure I represent all the layers of Andean cooking."

Back in the UK, I crave the beauty of Arequipa and the warmth of the Andean people; the sky looks dull and London feels disappointingly flat. But thanks to Morales and his team, at least I'll still be able to get a taste of true Andean soul food, and I'll raise a few glasses of chicha to that. 

Visit andinalondon.com for more info. 'Andina: The Heart of Peruvian Food' by Martín Morales is out now, published by Quadrille. Lydia Winter travelled as a guest of PROMPERÚ. For more information visit peru.travel

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