Boil the mutton along with bay leaves, cinnamon, cardamoms, cloves, dry red chilies and 1 cup water till done. (You can pressure cook for 20 minutes on a low flame after the first whistle).
Heat 2 tbsp. oil and fry the ginger and garlic for a minute. Then add 3/4 of the onion and saute till light brown.
Add the salt, 1/2 tsp. turmeric powder and coriander powder. Mix everything well and keep aside to cool. Grind to a fine paste along with the red chilies that was boiled along with mutton.
Dry roast the gram flour, cumin powder and rest of the turmeric powder till you get a nice aroma. Add the buttermilk and bring it to a boil. Simmer on a medium flame till it slightly thickens.
Now add the ground paste and the mutton stock. Mix well and bring it to a boil. Simmer for another 2-3 minutes.
Add the mutton and cook, covered for another 2 minutes or till you get the desired consistency.
Heat the remaining oil in another pan and temper with cumin seeds. Saute for a few seconds and add the remaining onion.
Fry till light brown. Pour this tempering over the mutton gravy and stir well. Garnish with a mint sprig.