Fragrant aged basmati rice layered with spiced meat, saffron-infused milk, and sweet caramelised onions, sealed and slow-cooked in dum style.
Coat the mutton with yogurt, ginger-garlic paste, half the birista, and salt; rest 2 hours.
Boil the rice in salted water until three-quarters done; drain.
Spread the marinated mutton and fried potatoes in a heavy pot; blanket with rice and nestle in the eggs.
Pour the saffron milk and ghee over the top, seal with dough, and cook on high 5 minutes then low 40-45 minutes.
Rest 10 minutes sealed; open, fluff gently, and serve each plate with a potato and an egg, Kolkata-style.