Marinate the mutton pieces with ginger-garlic paste, turmeric powder, red chilli powder, Kashmiri red chilli powder, coriander powder, cumin powder, salt, and 1 tbsp of mustard oil. Leave it for half an hour.
Put a pan on the stove and switch it on. Pour oil into the pan.
Once the oil gets hot, add sliced onions to the pan and continue stirring.
Add ‘whole spices for flavoring’ (except nutmeg) to the pan and continue stirring. Fry the onions until the color changes to brown.
Add the mutton and mix well with the fried onions and whole spices. Place a lid on the pan. Reduce the flame and allow the meat to cook for a few minutes.
Open the lid, stir, and place the lid back on.
You need to remove the lid and stir the mutton every few minutes to avoid burning at the bottom. You don’t need to add water at this stage as the mutton will release water. As soon as the mutton starts getting tender, it will release oil.
Now it is time to switch off the stove and transfer the curry to a pressure cooker. You can continue cooking in the pan, but it will take a long time as the dish is done in a slow cooking method.
Add some hot water to the cooker. Pressure cook the mutton on low heat until it is done. Usually, it will take just half an hour or five whistles to prepare the dish in the pressure cooker.
Open the lid and add fried potatoes to the curry. Cover the cooker and pressure cook again. Turn off the stove after two whistles.
Transfer the mutton curry to the pan. Cover the lid and let the curry simmer. Give a final touch by adding nutmeg powder and homemade garam masala. Bengali Style Mutton Curry is ready. Serve it with steamed rice, Bengali pulao, luchi, parathas, or pulao.