For the Cake:
Preheat oven to 350F. Line mini muffin pans with 36 liners. Set aside.
Mix together the flour, baking powder, soda, salt, and spices. Set aside.
In a separate bowl, with an electric mixer, combine butter and sugar until light and fluffy.Add in egg, pumpkin puree, dry ingredients, and then milk.
Fill each lined cup and bake for about 15 minutes or until toothpick comes out clean. Cool <b>completely</b> before frosting.
For the Frosting:
Beat butter in large bowl with electric mixer on medium speed until light and fluffy. Add vanilla and melted chocolate; mix well.
Stir cinnamon into confectioners' sugar. Gradually add to butter mixture, beating until well blended after each addition and scraping sides and bottom of bowl frequently.
Beat in milk until light and fluffy. If frosting is too thick to spread, gradually beat in additional milk. Store in refrigerator up to 2 weeks. Rewhip before using.