Grill chicken under broiler for 10 minutes. Set aside. In food processor, chop fine the nuts, blend in garlic, shallots, ginger, salt, turmeric, tamarind liquid, brown sugar, and chiles to form a smooth paste. Heat oil in skillet and stir-fry over moderate heat for 2 minutes. Add coconut milk, galangal, and lemon slice and cook for 10 minutes. Add chicken and cook over low heat for 30 minutes. Serve over rice.