To begin, soak the red chillies in warm water for 2-3 hours or overnight. The original recipe uses the Mathania chillies. If they are not available, you can use Kashmiri red chillies that I have used. Just make sure they are de-seeded. Once softened, add about 2 tbsp of water and blend into a smooth paste. Keep aside.
To marinate, take the mutton in a large bowl. Add the curd, ginger garlic paste, cumin powder, coriander powder, turmeric powder and salt.
Add the red chilli paste. Mix until the mutton pieces are well coated. Keep aside to marinate for at least half an hour.
Heat mustard oil in a pan to the smoking point and let it cool a bit. Add in a bay leaf and the whole garam masala. Saute until they crackle.
Add in the finely sliced onions and saute until translucent. Add in ginger garlic paste and saute for a minute.
Add in the marinated mutton and sear on high heat until the oil starts appearing.
Add enough water. Check the salt and add more in required. Cook until the mutton is tender. You can also pressure cook it for 4-6 whistles depending on the size of the mutton pieces.
Once cooked, add in ½ tsp garam masala powder for added flavor.
The Rajasthani Laal Maas is ready to serve. Garnish with chopped coriander leaves and garam masala. Serve with bajre ka rotlas or chappatis.