Pureé bananas in blender or food processor. In medium bowl, beat pureéd bananas, eggs, sugar, butter and vanilla until well blended. Stir in chocolate chips and nuts.
In large bowl, combine flour, baking powder, cinnamon and salt. Add to banana mixture and stir until just blended. Spoon into well greased or paper-lined muffin cups.
Bake at 350 degrees for 25 to 30 minutes. Makes about 12 muffins.