If using dried chilies, soak in warm water for 10 minutes. Blend into a paste with a splash of water.
- Heat oil in a large pot over medium-high heat. Sear lamb in batches until browned on all sides. Remove and set aside.
- In the same pot, add onion and sauté until golden. Add garlic, ginger, and chili paste. Cook for 1–2 minutes until fragrant.
- Add curry powder, cumin, coriander, turmeric, paprika, and tomato paste. Cook for 2–3 minutes to toast spices.
- Return lamb to the pot. Pour in coconut milk and enough water or broth to cover. Season with salt and pepper.
- Bring to a boil, then reduce to a gentle simmer. Cover and cook for 1.5 to 2 hours until lamb is fork-tender. Stir occasionally.
- Uncover during the last 20 minutes to thicken sauce if desired. Adjust seasoning to taste.
- Garnish with fresh cilantro or Thai basil. Serve hot with steamed rice or naan. Add lime wedges if desired.