Tsering has finally decided he wants English lessons after all and has taken to turning up in the evening. Last night he invited me to his place instead, to sample his cooking. It was excellent as before and I took the precaution of watching how he made Himalistani curry. He sliced, expertly and with no chopping board, onions, garlic, peeled potato and carrot, and tomatoes into a wok, roughly cut up some large chillies (each sliced in four lengthways and cut in half), covered them in water, added a couple of spoonfuls of oil and some salt and set them to boil. (The chillies are treated as a vegetable and are the only essential element; a curry with no other vegetables is the national dish.) Then we sat and chatted, and after 15 minutes or so he tasted it for salt and sliced in a few small pieces of local cheese, of which he has large supply, and when this had dissolved into the water, the curry was ready. (He also added a slice of processed cheese; but this is not, I think, essential.)
I made my own the next evening, which while not quite up to Tsering's standard was reasonably successful. I think I shall make Himalistani curry frequently in future. It's extraordinarily low-effort, delicious, and consisting as it does almost entirely of fresh vegetables, a great deal healthier than most of what I eat at home.