Preheat the oven to 350 degrees.
In a medium bowl, beat together butter, sugar, egg and vanilla until fluffy.
In a separate bowl, whisk together flour and baking powder. Then add this mixture to the butter mixture and beat until well blended.
Next, we will shape the dough into 3 different sizes of cookies. (Each cookie will be rolled into a ball.)Use a rounded 1 teaspoon of dough to make 1 small ball. Then you will use 2 rounded teaspoons of dough to make a middle size ball. And 3 rounded teaspoons of dough to make a large ball. You want to have the same number of each size of ball. You should be able to make at least 15 balls of each size.
Place the small balls onto 1 parchment paper lined baking sheet. Use a glass to gently flatten them a little. Place the medium size balls on another sheet and again press them down gently. And place the large balls on a separate sheet and press them down slightly. (The different sizes of cookies should bake on different sheets as they will not bake at the same rate.)
Bake until the bottoms are just golden. Small cookies will take 4-6 minutes. Medium will take 6-8 minutes. Large will take 8-10 minutes.
Remove the cookies from the baking sheets and allow them to cool completely on wire racks.
Prepare the frosting while the cookies are cooling.
In a medium bowl, beat together powdered sugar, and butter. When this is well creamed together, beat in the milk and vanilla (and food coloring if desired).
Use the frosting to “glue” together the 3 cookies (largest on the bottom, then middle sized, then the smallest on top) to make a christmas tree or snowman. Pipe (or spread) icing onto the top of the largest size cookie and place the middle size cookie on top. Pipe (or spread) icing on the top of the middle size cookie and place the small size cookie on top. Then continue decorating with the icing.