Wash the mutton pieces, drain and set aside. Boil the potatoes in a little water, with salt to taste, till half-cooked and still firm. Infuse the saffron in the boiling water and set aside. Pan-fry 1 chopped onion in 15 ml (1 Tbsp) of the butter and set aside.
Place the mutton pieces in a large mixing bowl and add the buttermilk, green chilli, garlic and ginger paste, dhania, salt, red leaf masala, ground jeera, chilli powder, mother-in-law masala, wet khokni masala and turmeric. Mix thoroughly, ensuring that all of the mutton pieces are covered in the marinade. Set aside for 1 hour.
Rinse the rice in a colander, drain and place in a large pot on medium to high heat. Add water to reach halfway and add 45 ml (3 Tbsp) salt. Boil till half-cooked (the rice grains should be firm). Transfer to a colander and rinse under cold running water. Drain and set aside.
To a large pot on medium to high heat, add the ghee and heat. Add the remaining chopped onions along with the jeera seeds, mustard seeds, bay leaves, cardamom seeds and cinnamon and braise till golden in colour. Add the marinated mutton pieces along with the marinade, the 60ml (1/4 cup) of water and simmer on medium heat for about 30 minutes, or till the meat is tender and cooked.
Arrange the potatoes between the mutton pieces and spoon the rice directly on top. Pour the fried onion with the melted butter over the rice, and lastly pour the cup of water containing saffron over the rice and onions. Steam, covered, for 35 minutes. Remove the heat and serve dhai and tomato and onion salad.
Note: All akhnis and breyanis should be dished from the bottom up.
Variation: The mutton may be substituted with chicken pieces (thigh, drumstick, wing and breast,) and prepared in exactly the same manner. Note that the breast portion should be halved.