Preheat oven to 350°. Puree bananas in blender. In medium bowl, beat pureed bananas, eggs, sugar, butter and vanilla until well blended. In large bowl, combine flour, baking powder, cinnamon and salt. Stir in chocolate chips and nuts. Make well in center of dry ingredients. Pour in banana mixture. Mix until just blended. Spoon into well-greased 2 1/2-inch muffin cups. Bake 25 to 30 minutes. Remove from pan. Makes about 12 muffins.