Preheat oven to 180 degrees C. Line muffin tray (cups ~6cm in diameter) with paper patty cups/muffin cases.
In large mixing bowl mix the butter, sugar, brown sugar, egg and vanilla until well combined. Add apple sauce then blend well.
In a separate bowl stir together flour, cocoa, baking soda and cinnamon, if desired. Add to butter mixture mixing well. Stir in chocolate chips. Fill muffin cups 3/4 full with batter.
Bake at 180 degrees C for 22 to 25 minutes or until wooden pick inserted in centre comes out almost clean. Cool slightly in pan on wire rack. Sprinkle muffin tops with icing sugar, if desired. Serve warm.