Preheat oven to 350 degrees F (175 degrees C). Line muffin cups (2-1/2 inches in diameter) with paper bake cups.
In large mixer bowl, beat butter, sugar, brown sugar, egg, and vanilla until well blended. Add applesauce, blend well.
In a separate bowl, stir together flour, cocoa, baking soda, and cinnamon, if desired. Add to butter mixture, blending well. Stir in chocolate chips. Fill muffin cups 3/4 full with batter.
Bake at 350 degrees F (175 degrees C) for 22 to 26 minutes or until wooden pick inserted in center comes out almost clean. Cool slightly in pan on wire rack. Sprinkle muffin tops with confectioners' sugar, if desired. Serve warm.