Combine yogurt, paprika, garam masala, and turmeric powder in a bowl.
Add in lamb pieces to marinate overnight.
Puree ginger, garlic, and shallots into a paste.
Heat ghee in a pan.
Roast pureed paste until aromatic.
Add in cardamom pods, cloves, black peppercorns, cinnamon stick, and cumin seeds and continue roasting for another minute.
Add in tomato paste, and roast for another minute.
Add in diced tomatoes and marinated lamb pieces.
Transfer to a slow cooker and cook on low for 8 hours.