Chiang Mai was the first city we visited in Thailand, some fifteen years ago now. I still remember it for my first encounter with Thai food that was not from the menu of “20th century British Thai” (red, green or massaman curry and pad thai). A bowl of khao-soi in the street market, a beautiful amber soup with bright flavours of lemongrass and kaffir lime, earthy turmeric, creamy with coconut milk and lifted with a good hit of rusty red chilli. The noodles were so good they didn’t need any meat or veg, and on the side was a platter heaped with various local herbs I’d never seen back in the UK along with sliced shallot and crunchy bits of deep-fried noodle, all to scatter over the fiery soup to your taste. I think we had khao-soi three or four times over our five days in Chiang Mai.

So of course we were straight down to the new Thai place near Oxford Circus, Khao-So-I, named for and specialising in the dish. It’s got good pedigree, being the first overseas outpost of Chef Win whose restaurants in Thailand are very well regarded.

Inside they’ve got table seating and a long kitchen counter, where we perched on high but comfortable enough stools. This isn’t a place for a long and languid meal anyway, the dishes come out pretty prompt. The interior is smartly decorated in cool modern earth tones, stripped back simplicity and none of the loud bling you might associate with Thai dining. We start with a couple of very good cocktails; a margarita with wonderful notes of pandan and kaffir, and a Nimman 75 with floral lychee kept in check by dry champagne and good gin.

We started with a couple of small dishes. One was a delightful salad of young jackfruit, fresh with good flavours of kaffir lime and other herbs I’d have trouble identifying, pepper up with just enough dry chilli to build heat as you eat. The other was fermented fatty pork and egg, wrapped in banana leaf and roasted in there. The sticky, porky concoction inside the leaf was fragrant with Thai flavours tangled up with pork fat, very moreish.

Unless you want a meal of starters, you’ll be having khao-soi for main; it’s not so much a signature dish as the only dish on the menu, albeit served with almost a dozen variations in topping. I went for a mix of torched and braised beef, while Maureen chose the tofu. The tofu was nice, sturdy with a bit of crisp to the edges. If I came back, I’d skip the thin slices of scorched chuck-eye and stick with the braised shank. It was marinated and braised to a sweet and almost jammy stickiness, I could have had a plate of it happily. But of course the khao-soi soup and noodles are the main event. The soup was exactly as I remember it, just the right level of heat, made silky and rich with coconut milk, fragrant with all those northern Thai herbs and spices. The noodles are chunky and toothsome, not as thick as udon but thicker than ramen. And there’s sides of chopped herbs, pickled mustard greens, chilli flakes and coconut milk to stir in to taste, along with the little bowl of deep-fried crispy noodle bits for topping.

I loved my bowl of khao-soi at Khao-So-I and you should go along and try if you’ve never had the original stuff in Thailand, because this is it. That said, it’s their only thing and it averages around £25 a bowl, topping up to £35 per person for a meal of starter-and-main. So it’s priced a bit higher than top-notch ramen. Probably deservedly. So I’ll be popping back next time I really need a khao-soi fix.