To prepare the same curry with mutton, the only thing you need to do is to cook the curry for 3 or 4 whistles instead of 1 whistle. And I also prefer not to add potatoes at the same time. I usually cook the potatoes separately and then add them to the mutton curry. You can marinate the mutton pieces with a small amount of ginger and garlic paste, salt and lemon juice before adding to the pressure cooker. Rest all the steps and ingredients remain the same.
This curry can also be prepared in a saucepan or a wok too.