It's a restaurant I've visited nowhere near as often as I should have, where you can get a five-course tasting menu of sublimely inventive and thoughtful food for less than $100 (and at a "test kitchen" on Tuesdays, eight courses for $80). If you haven't been, make it the second-to-next restaurant you go to.
The next one, though, should be this new place, which occupies the space below street level that was briefly home to the Mandarin Dumpling Bar.
I remarked in a review of Mandarin that it was part of a trend at the time of "putting the ritz on the basics of Asian food", and at first glance, you might think Cassia is doing the same thing: an acknowledged fine-dining maestro turns his attention to the cuisine of India (thoughtfully, he left it until a few weeks after I wrote that Indian fine-dining was virtually unknown here).
But there's a significant difference: with the exception of basic accoutrements such as naan bread and rice and a side of braised beans done with grated coconut in the South Indian foogath style, there is nothing here that any regular patron of the local curry house will have come across.
Rather, Sahrawat, born and raised in Chandigarh in the Punjab, inhales the essence of his native land and goes to work making food his way.
So the scallops (with a curry emulsion) come with foie gras and apple; the menu tells you to expect burata (a buttery ball of buffalo mozzarella) with a dish of roasted potato and cauliflower; there's kumara with the "Delhi" duck; and there's a short rib of beef, a meat not commonly encountered in Indian cuisine because it's taboo to Hindus, though widely eaten by other religious groups.
Sahrawat told me the day after my visit that the toying around was equal parts creativity and pragmatism. Burata has none of the dryness that can bedevil even the best paneer, as Indian cottage cheese is known, and it lends a creamy texture to the classic combination of potato and cauliflower.
In the event, we didn't actually try that, but what we did have was a revelation.
We opened with kulcha, a little like pizza bread but laced with onions, with which we mopped up an explosively tasty coriander dip.
Fennel brioche were like tiny slider buns with tenderloins of chicken that had deliciously caramelised on the edges in the tandoor oven. The salsa-like kuchumba and yoghurt added respectively zinger and cooling tastes on top.
Fish described as "pickled" had been marinated before being baked and served on a bed of chickpea masala.
The crowning touch was a puri - like a tiny kina shell - filled with potato curry, which was topped up at the tableside with tamarind water: you eat it in one bite and it's heaven.
Sensationally meaty and tender lamb chops, coated with fenugreek and tandoori-baked, came with onions two ways - fried rings and pickled - with coconut lending sweetness.
The fried eggplant with mushrooms was bathed in a minty sauce of milk curd enlivened with chilli. A Bengali-style fish curry featured tiny flash-fried kale leaves that melted on the tongue in a dense burst of flavour.
All this is to say nothing of sublime desserts: a passionfruit icecream made of rice milk, with pineapple and mango sorbet, was the standout for me, but the Professor, a stern judge of desserts, said the cardamom panna cotta and the chocolate kulfi (India's answer to custard cream) should not be ranked lower.
It's worth mentioning that this is not an expensive night out considering the chef's pedigree: $60 a head (drinks extra) would be a maximum spend.
For that price you get Indian food as you've never had it because it didn't exist until now.
Enjoy.
Verdict: Sid Sahrawat does a taste of home, with spectacular results.
