Do Piaza (Lamb with the Onion Added Twice)

Variations

• Vegetarian: made with paneer or chickpeas. With no meat stock, brown the first onion harder to fill the gap. ko.wikipedia records the vegetarian version.
• With prawns or chicken: they cook fast, so cut step five to 15 minutes and put the second onion in almost with the meat.
• Hyderabadi: the court kitchens where the dish developed, and that side is explicit about souring it — ko.wikipedia names mango, lemon juice and cranberry. The last tip is about that.
• Skimming: a generous hand with the ghee in the first onion leaves fat floating at the end. Skim it or leave it; left on is the traditional look.
• The British curry-house do piaza usually has tomato in it and puts the onion in once. It shares the name and not the structure the first tip is about.

Tips

• The name is the method, and that is the whole dish. The onion goes in twice, and what differs is not the amount but the state. The first 500g spends thirty minutes going brown and collapsing to a third of its volume, losing its shape entirely — at that point it is no longer a vegetable but the body of the sauce. The second 400g goes in as big petals for the last fifteen minutes and stays a vegetable. You should be able to tell the two apart on the plate.
• Kung pao chicken writes down the nearest shape, for starch. That page says "the starch is in this pan twice, doing the two jobs that guide keeps apart. Step 1 puts it on the chicken, where it must stay soft and wet and must never colour. Step 2 mixes more of it into the sauce, where it must thicken. Same tin, ten minutes apart, opposite objectives". The difference is this: there one ingredient does two invisible jobs, while here the second lot is meant to stay visibly itself.**
• The first onion is body, not aroma. Blooming spices starts from aroma being fat-soluble — "Stirred into water only some of it comes out; hit with hot oil, far more is extracted and it spreads through the whole dish" — and its dial is how far the cells are broken. This dish sets that dial at both ends in one pot. Cut the thirty minutes short and the sauce stays thin with a raw onion taste through it.
• Do not stir the second onion in. Lay it on the surface and put the lid on so it steams. Stirred down into the liquid it collapses within the twelve minutes and becomes indistinguishable from the first lot.
• Tear the petals apart rather than slicing them. Quarter the onions and pull the layers apart by hand: they separate at an even thickness with clean faces. Sliced, the thin edges go first (knife skills).
• Split yoghurt is not a failure here. It looks broken at step four and comes back smooth over the hour and twenty minutes of gentle simmering. What it must not do after step five is boil (dairy and heat).
• Acid last, off the heat. ko.wikipedia records that souring matters in this dish — mango, lemon, cranberry. Its job is to answer the sweetness of nearly a kilo of onion and five tablespoons of ghee, and added during the simmer it cooks away and leaves only the weight (balancing flavour).