You can tell how cool Casa Negra's going to be when you check its website and there's TV footage from the 1950s, of Salvador Dali on What's My Line?, bamboozling the blindfolded guests by answering "Yes" to all their questions.
The owners of Casa Negra like a drop of surrealism. The décor is a riot of Latino-fiesta colours, with touches of English restraint. The black-and-wood floor tiles are obscured by a carpet from your granny's twilight home. The walls and wood panelling are painted in Stygian-black gloss, contrasting with the bright hues of the Sol bar – poster-paint red, green-and-white candystripes. The dining room is full of larky pictures (one of Frida Kahlo, her eyes obscured, punk-style, by the words, "Thank God it's Frida") and an incongruous English-country-house log-pile is stacked against a window. The whole place has a jolly, Mexican-seaside vibe, not something you often find in trendy Shoreditch.
This place is the site of the old Great Eastern Dining Room; the owners seem to have called in local designers and suggested they impose a lot of faux-Mexican-osity on the old place. It's the new sister establishment of La Bodega Negra, a New York-style café-taqueria which has enlivened the Soho landscape for a year with its street food and cray-zee décor, all Day of the Dead puppets, wrestling masks and other Mexicano impedimenta.
Only a madman could ignore the gorgeous bar on a boiling July night, so my children and I tried a few cocktails. Their Casa Margarita is a decoction of El Jimador tequila, fresh lime and orange sherbet liqueur and packs a wallop. Max needed a thirst-quencher and tipped a pint of Vote Pedro (he's a Napoleon Dynamite fan) down his throat: tequila, elderflower liqueur, cucumber, mint, lemon and soda – intensely satisfying. Sophie's non-alkie Jax Colada (coconut, pineapple, lime and passionfruit) bounced with healthiness.
On the menu, a dozen familiar words swim before your eyes in a score of permutations: chorizo, tortilla, quesillo, jalapeno, chipotle, ranchero, avocado, salsa, habanero – oh and chilli, of which six or seven variants are on offer. What else would you expect from Mexican street food? But the American chef Brad McDonald is a sophisticated guy – his CV includes Noma in Copenhagen and Thomas Keller's Per Se in New York – who has clearly fallen in love with Mexican cuisine.
The charming waiting staff ferried small plate after small plate of things to fight over. Beef tartare on a tostado with lemon, chilli and onion, lifted by slivers of avocado. Chihuahua and Monterey Jack cheese smokily delicious like a sexy mozzarella, served with homemade chorizo. Cochinita pibil, a traditional Mexican dish of pork marinated in orange juice, given colour and flavour by the achiote flower, and slow-braised in a banana leaf, was earthy and unctuous, served with black beans.
The only disappointment was pescado – grilled sea bream served with chipotle, jalapeno and cabbage. The subtle bream felt like a weak-kneed, albino-eyed, gringo wuss among all this manly, meaty company. Overwhelmed by the spices, it tasted… sweaty.
Main courses brought an ensalada verde, overpriced at £10, throwing together avocado, lettuce, radish, tomato and cheese; it was, said Sophie, refreshing after all the beef and cheese, but not interesting. The green goddess dressing (which is Californian, not Mexican, though it originated in Versailles as sauce au vert) lacked excitement. Max's skirt steak arrived sliced and smothered in habanero salsa. I was surprised to learn it had been slow-cooked by the sous vide method (you won't find many water-baths in Mexico City backstreet kitchens) then flash-fried on a flat griddle. It was tightly textured and toothsome.
Fire-roasted sweet potato was a beautiful apricot hue and tasted sweet as kumquats. My Pollo Dorado con Chilito was spicy fried chicken, more Maryland than KFC, served with about a kilo of cabbage and carrot slaw: two immense chicken legs in batter, the flesh yielding, the blanket of batter rather unpleasantly chewy. We shared a side-dish of pinto beans with bacon, tomato and jalapeno until we realised we were full up.
I managed a mouthful of flan, the dark Mexican crème caramel, which was teeth-rottingly sweet. "I feel," said Max, "as if I've been eating for three days."
Me too. Casa Negra is a colourful and characterful sibling to the flamboyant Bodega; but both places make you wonder how consumers of street food, when they leave, make it as far as the traffic lights.
Casa Negra, 54-56 Great Eastern Street, London EC2 (020-7033 7360). About £110 for two, with drinks