Preheat oven to 350F. Cream butter and sugar. Mix in egg and banana. Stir together flour, baking powder, baking soda, salt, nuts and chocolate chips. Add this mixture to creamed mixture alternately with buttermilk. Stir until just blended. Pour batter into a greased and floured loaf pan (9x5x3 inches). Bake for 65 minutes, or until bread tests done. Cool in pan for about 5 minutes, then turn out on a wire rack. Makes 1 loaf.