Puree bananas in blender (1 cup). 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. Make a well in the center of dry ingredients. Pour in banana mixture. Mix just until blended. Spoon into well greased 2-1/2 inch muffin cups. Bake in 350 degree oven 25 to 30 minutes. Remove from pan.