Delhi-Style Lamb Cooked with Potatoes

This is one of the everyday meat dishes that I grew up with in Delhi. I still love its homey taste and have a particular weakness for its sauce, which seems to combine all the goodness of lamb, potatoes and tomatoes as well as the cheaper, commoner Indian spices: cumin, coriander, turmeric and cayenne pepper. I like it with rice or an Indian bread and Gujarati-style green beans.