Heat pressure cooker over medium heat and brown lamb piece in batches, set aside. Drain off oil and add butter and onions to the pan and saute until translucent. Now add scallions, jalapenos, ginger and saute for a few minutes more then add garlic and curry powder. Saute until you smell the curry then add tomatoes, lamb and water. Bring this to a simmer. Put lid in place and bring up to high pressure, lower heat to maintain pressure. When time is up (15 minutes) take lid off and bring stew back to a simmer to reduce juice. Season with salt and pepper to taste. Serve over rice and garnish with cilantro.
Grind all spices in a mortar and pestle or in a spice grinder. Store in an airtight container.