Heat oil in a pressure cooker. Add in the onions and saute till wilted.
Add in the ginger garlic paste, green chillies and saute till the raw smell is gone.
Add in the coriander and black pepper powders and saute for a couple of minutes.
Add in the mutton and around 1/2 cup water. Add salt to taste.
Cook for three whistles or till done, and switch off.
Meanwhile, grind the coconut and cashew nuts till smooth, adding a little or whole of the soaked water.
Once the mutton is done, switch on the flame, add in the ground mixture, garam masala and coriander leaves and bring it to a boil.
Add the tomatoes, switch off the flame.
Close the lid and set aside undisturbed for 10 minutes.
Serve warm with rice or porottas.