Rince the mutton pieces well and keep aside to drain any excess water.
In a non- stick pan, heat some oil on medium heat and add cumin seeds. Once cumin splutters, add onions and sauté for 5 mins. Then add the chopped ginger and garlic. Sauté until the onions turn translucent.
Now add the diced potatoes and sauté till it turns slightly brown. Remove the potatoes and keep aside.
Reduce the heat, add the spices (except garam masala) and roast till it leaves a good aroma.
Now take a pressure cooker and transfer the onion mixture.
Add the mutton pieces. Add a splash of water.
Allow it to slowly cook, for about 10-12 whistles or till the mutton pieces are well cooked and coming off the bone easily.