"MADAME, THE DUM pukht kakori." My waitress delivers her line in a reverent half-whisper, the sort of practised hush used to announce a president or a Hollywood heavyweight into the room; a VIP in any case, or, in this instance, a VIK – a Very Important Kebab. This, she says without saying it, is a piece of meat that demands contemplation and respect. "It was made for the last king of Lucknow," the waitress adds, "who lost his ability to chew, but not his love of kebabs."

She hovers expectantly. I take what I hope is an appropriately timed pause for meditation on minced lamb, then lop off a morsel and pop it in. This is ridiculous. The meat hasn't been minced: it's been pulverised to please the palate of that gnasherless 19th-century royal. "Melt in the mouth", the menu says, but it feels like it melted long before it ever touched my tongue, leaving behind some sort of clove, cinnamon and saffron-spiced near-liquid silk.

But what else to expect when dining in Kolkata? The capital of West Bengal is widely considered the food centre of the entire subcontinent. This is no small claim to fame, considering food is the cornerstone of Indian culture. The country may be as split as the Scotland vote – a seething, teeming bundle of castes, improbable languages (Malayalam?) and religion – but there's one thing everyone can agree on, and that's their love of eating.

A crowd watches hungrily as parathas are loaded with kebab meat, fried egg, onions sizzled in spices, pepper and lime

Family meals spend days simmering in pans; street hawkers satiate the passing hungry hordes. Each state brings a new favourite plate. I've joined rickshaw drivers jiving for jalebi in Agra, dabbled with breakfast dosas in Kerala and crammed in zingy, vinegar-sloshed Goan curries. And in Kolkata, with everything from posh restaurants such as Dum Pukht – where I'm losing myself in that lamb-fuelled reverie, and the chefs are all descendants of royal court cooks – to what is considered the country's cheapest and most diverse street food, the determined scoffer in me has arrived ready to eat.

Central foodie stretch Park Street is many a visitor's first stop, and it's just off here that I find Kusum's, my hotel concierge's top tip for a kathi roll - a sort of Indian burrito that Rick Stein once called "the perfect street food". He's not wrong. A crowd watches hungrily as the guys behind the open-air counter load pancakey parathas with kebab meat, fried egg, onions sizzled in spices, a few shakes of black pepper and a squeeze of lime. (For those nervous about eating off the street in India, just go wherever the locals are congregating and order whatever they're ordering – it's the best way to discover exotic eats without regretting it later.) Every bite of my packed roll gives the kind of warming satisfaction only a hefty, fried street snack can – and all for the princely sum of 45p.

Eat on the street

Delicate constitutions will be relieved to hear Bengali food is seldom spicy. Kolkata's street carts instead tend to serve up variously intriguing chutney-soaked chaat – chaat being a catch-all for savoury roadside snacks, ordinarily involving fried dough, then scattered with manifold combinations of potato, lentils, sweet curd (yoghurt) and the like. I'm told a joint called Ridhi Sidhi on Lord Sinha Road offers several stalls serving all manner of things popping and crackling in pans; a stop-start cab ride through the heaving streets later and, along with an expectant belly, I've arrived. The day is September grey, but the heat is wet and close.

I try puchka (also known as pani puri or golgappa, about 10p), one of the country's most iconic nosh-as-you-walk nibbles and a specialty of Kolkata. A hollow, round, puffed-up crisp (the 'puri') snaps under my teeth to release its contents: a spicy deluge of mashed potato and tamarind water.

At the fish market, great slabs of flesh the size of my torso are displayed on banana-leaf mats, while monstrous prawns lie draped on crushed ice

It's an explosion of taste and sensation quite unlike anything else. I also try a sloppy plate of what's best described as a chopped-up potato doughnut (ring-shaped, with a crispy fried outer and a buttery mashed inner), smothered with sweet curd, spicy moss-green coriander chutney and little bits of dried gram-flour vermicelli. Sounds odd, looks odder – but, at 20p, it tastes incredible, a delicious mess of sweet and savoury, hot and sour, crunchy and soft.

This motley mish-mash is as expressive of Kolkata's history as it is of the cuisine. Formerly the capital of British India, there are vestiges of Raj-time glory: grimy, once-grand baroque buildings; leaf-lined, wide tarmac roads; the smack of leather on willow at Eden Gardens Cricket Ground. This past struggles for influence with both present and future, as the skeletons of future towers loom over slum communities built under bridges.

Crossbreed cuisine

But these dichotomies have always defined Kolkata. Today, it's the modern, commercial, educational and cultural centre of East India; and yet, tucked close to the border with Bangladesh and spitting distance from Bhutan, Nepal, Tibet and China, the city – population 14.1 million – also swells with poor migrants. Weary men grind at the pedals of bicycles pulling implausible loads – a trailer piled high with gas canisters, an almost literal ton of bricks – weaving laboriously between the luxury cars as they go. That's why you'll find such a lively culinary culture: the business suits want refined, AC-cooled restaurants, the minimum-wage workers need cheap eats on the go, and you're as likely to find chow mein and Tibetan dumplings on menus as you are tandoori.

Seafood is also a staple of Bengali cuisine, given the proximity to Diamond Harbour, near where the Bay of Bengal meets the Hooghly River. Just as abundant are freshwater catches from the rivers and lakes of the Ganges Delta. But don't expect to be ordering up your standard Brick Lane prawn vindaloo or fish tikka; regional specialties include smoked river fish bhakti smothered in a mustard and green chilli sauce.

A walk around Kolkata – in pictures

Predictably, it's fantastic; the sauce packs all that rich mustard flavour, but none of the up-your-nose-and-into-your-brain pain. One of my favourite days in the city is a trip to the fish market, where great slabs of creatures the size of my torso are displayed on banana-leaf mats; monstrous prawns are draped on crushed ice. In several baskets, still-alive koi carp jump, struggling for breath. It doesn't get much fresher than that.

While you can generally indulge in Kolkata's finest food experiences for less than £1 a pop, for my last night I can't resist Peshawri. The signature restaurant of the business-swish ITC Sonar hotel, it's an almost-exact replica of Delhi's most famous restaurant, Bukhara, also owned by the ITC hotel group. Everything is cooked in clay tandoors set to different temperatures (some up to 300-400ºC), which takes great skill for the cooks to maintain. I treat myself to signature dish Sikandari Raan, a whole leg of lamb marinated in malt vinegar, black cumin and red chili. This isn't just lamb so tender it falls apart at the touch of my fork; the flesh has already been softened into submission and is slumped into piles around the bone by the time it arrives.

The trick in Kolkata, then, is simple: never discriminate. Dive in among the clamouring rabble at street stalls by day, then fine-dine your way through elegant evenings. The city has more than one side to explore – make sure you eat it all up. ■

Air India flies from London Heathrow to Kolkata, via Mumbai, from around £440 return. Rooms at the five-star ITC Sonar hotel start from around £90 per night, if booked in advance. See airindia.in and itchotels.in