Beat butter and cream cheese in a medium mixing bowl with an electric mixer on medium speed for 30 seconds. Add 1 1/2 cups powdered sugar, cocoa powder, baking powder, and cinnamon; beat until combined. Beat in egg and vanilla. Beat in as much flour as you can with the mixer. Stir in remaining flour with a wooden spoon. Divide dough in half. Cover and chill for 1 hour or until easy to handle.
Roll each portion of dough on a lightly floured surface until 1/8 inch thick. Cut out with a floured moose-shape cutter. Arrange cutouts 1 inch apart on an ungreased cookie sheet.
Bake in a 375 degree F oven for 8 to 9 minutes or until edges are set. Cool on cookie sheet for 1 minute. Transfer to wire racks to cool completely. For the icing, stir together 2 cups sifted powdered sugar and 2 tablespoons milk. Add additional milk, 1 teaspoon at a time, until it reaches drizzling consistency. Use a decorating bag fitted with a fine writing tip to outline cookies with icing. Makes about 20.