In a large stand mixer bowl, beat together butter and sugar until light and fluffy. Add eggs in one at a time, then add in vanilla. Mix well.
Add flour one cup at a time. At the 3rd cup add in the baking powder, cinnamon, and salt, mix well.
Form dough into a ball and cover. Refrigerate for 30 minutes.
Preheat oven to 375 degrees. Roll the dough into 1" balls and place onto a prepared baking sheet. Flatten cookie with bottom of glass or your hand until 1/3 or 1/2 inch thick.
Bake for 7-9 minutes until edges are golden brown. Remove to cooling rack to cool completely.
To make the frosting, beat together cream cheese and butter until light and fluffy. Add powdered sugar 1/2 cup at a time until smooth.
Add vanilla. Add milk to thin out if necessary. Beat until light and fluffy.
Using a ziploc bag or piping bag, pipe frosting onto cookie, starting from the center and spiraling to the outside edge. Sprinkle with cinnamon. Enjoy.