Take the mutton pieces in a bowl. Add the beresta, cubed onions, ginger paste, garlic paste, turmeric powder, roasted cumin powder, coriander powder, red chili powder, black pepper powder, garam masala powder and 1/4 cup mustard oil. Give it a hearty mix.
Take a thick bottomed pan, transfer the mutton along with the marinade to the pan. Cook over a medium flame, with frequent stirring in between, till the oil starts getting released from the masala.
Continue to cook over a medium flame, another 60 minutes or so.
Heat ¼ cup mustard oil in small saucepan. When smoking hot, throw in the green cardamom, black cardamom, cloves and dry red chilies, allow the spices to splutter. Add chopped onion, garlic and fry till brown.
Add this to the mutton, give it a good stir.
Now add the radhuni powder, nutmeg powder and mace. Sprinkle in the salt. Mix well, continue to cook over a low to medium flame, stirring frequently in between to ensure that the masala doesn’t get burnt or stick to the cooking pan. If needed, feel free to add a splash of water. Continue to cook, another 30 minutes over a low flame till the mutton is tender.
Garnish with fried onions, serve hot.