Stir together flour, cocoa, baking soda and cinnamon, if desired. Add to butter mixture, blending well. Stir in peanut butter chips. Bake 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 powdered sugar, if desired.
12 to 15 muffins. Omit Peanut Butter Chips. Semi-Sweet Chocolate Chips. Hershey's is a registered trademark of. Add the Pumpkin Pie spice, sugar, milk, oil, and nuts.