Step 1) Combine onions, garlic, ginger, cinnamon, cardamom, black pepper, cloves, crushed red pepper, bay leaf and 2 tablespoons water in a blender or food processor. Blend until smooth.
Step 2) Heat oil in a large skillet. Cut up chicken into 1-inch pieces. Brown chicken, turning once, and remove with slotted spoon to a bowl. Refrigerate.
Step 3) Reduce heat to medium and carefully pour in spice paste. Stir and fry the paste for 5 minutes, stirring constantly. Add tomato sauce, 1/2 cup water and salt; bring to a boil. Cover, turn heat to very low and simmer gently 20 minutes, stirring occasionally.
Step 4) Add the chicken, along with any juices; bring to a boil and simmer 20 minutes, stirring occasionally. Stir in garam masala. Remove from heat and stir in butter and cream. Serve with Basmati rice or naan.