Meanwhile, make the crushed peas. Lightly blanch the peas in boiling salted water for one minute, then drain. Heat the butter and oil in a frying pan. Add the asafoetida and, as it foams, add the cumin seeds. When the cumin seeds crackle, add the chilli flakes and the blanched peas. Cook for 3-4 minutes, then stir in the stock (or water) and cream, and season with salt and freshly ground black pepper. Remove from heat and, with a wooden spoon, crush the peas. Keep warm while you fry the fish.