In a medium bowl, combine the lean mutton, non-fat Greek yogurt, turmeric powder, and half of the sea salt.
Allow the mutton to marinate for at least 30 minutes to naturally tenderize the meat.
Rinse the dry basmati rice under cold water until the water runs clear, then soak in fresh water for 20 minutes.
Parboil the soaked rice in a pot of boiling water for 5-7 minutes until it is 70% cooked, then drain and set aside.
Heat the ghee in a heavy-bottomed pot or pressure cooker and sauté the sliced red onion until deeply caramelized and golden.
Stir in the ginger paste and garlic paste, cooking for 1 minute until highly fragrant.
Add the marinated mutton to the pot and sear on all sides until browned and the yogurt has absorbed.
Add the garam masala, black pepper, and 0.5 cup water; cover and simmer on low heat for 35-40 minutes (or pressure cook for 15 minutes) until the mutton is fork-tender.
Layer the parboiled rice evenly over the cooked mutton mixture and sprinkle with chopped fresh cilantro and fresh mint.
Cover the pot with a tight-fitting lid and steam on the lowest heat setting for 10 minutes before fluffing with a fork and serving.