Cut lamb into 1 inch cubes. Melt the butter in a large stock pot, and cook the onion until softened, 8-10 minutes. Add the lamb and brown the meat, about another 8 minutes, stirring occasionally.
Add the ginger, pepper, salt, curry powder, and mint and cook another 5 minutes.
Stir in the milk and coconut milk, bring to a simmer and cook over low heat for one hour.
Stir in the grated coconut, lime juice and cream and cook another 5 minutes. At the very end taste for seasoning and add more salt if needed, then stir in banana and raisins. Serve with rice, crispy pappadums, and mango chutney if desired.