Preheat oven to 375 degrees and lightly butter muffin tin. Stir together dry ingredients. With mixer, beat butter and brown sugar until light and fluffy. Beat in eggs, then stir in vanilla, banana, and milk. This will look curdled, don'ts panic. Add dry ingredients and stir to combine. Reserving 2 tb each of nuts and chips, stir in remaining ingredients. Spoon into muffin tin, then sprinkle tops with reserved nuts and chips. Bake 30 minutes or until toothpick comes out clean. Cool in pan 5-10 minutes on rack. Remove and cool on rack.