1. In a bowl, cream butter and sugars. Beat in eggs, bananas and vanilla.
2. Combine flour and baking soda; add to creamed mixture just until combined. Stir in the walnuts and chocolate chips. Fill greased or paper-lined muffin cups half full.
3. Bake at 350° for 15-20 minutes or until a toothpick comes out clean. Cool for 5 minutes before removing from pans to wire racks.