Preheat oven to 350°F (180° C).
While the oven is preheating make the cookie dough. Cream together the butter and sugar until light and fluffy.
1 1/2 cups (333g) salted butter, 1 1/2 cups (345g) granulated sugar
Scrape the sides, add in the eggs, and vanilla extract. Beat until mixed.
3 eggs, 1 1/2 tsp vanilla extract
Scrape the sides and add in the flour, baking powder and cinnamon. Mix until thoroughly combined.
4 1/2 cups (684g) all-purpose flour, 3 tsp baking powder, 1 tsp cinnamon
Scoop out 1/3 cup of dough and roll into a ball. Repeat with remaining dough.
Combine the sugar and cinnamon in a bowl, separate out a few tbsp worth of the cinnamon sugar and reserve it for sprinkling on top of the cookie after frosting.
1/2 cup (115g) granulated sugar, 1 tsp cinnamon
Roll and press the cinnamon and sugar onto the cookie dough. Flatten the cookie dough gently so it is in the shape of a hockey puck. Repeat with remaining dough.
Arrange 6 cookies per pan. Bake at 350°F (180° C) for 14-17 minutes or until the centers of the cookies have puffed up and are no longer glossy.
While the cookies are cooling, make the frosting, by whipping the butter until smooth.
3/4 cup (167g) salted butter, room temperature
Add the powdered sugar, one cup at a time, adding a little bit of milk after each cup of powdered sugar to keep the consistency like a thick frosting.
4 1/2 cups (482g) powdered sugar, milk
Once you have added all of the powdered sugar, mix in the cinnamon thoroughly.
1-2 tbsp ground cinnamon
Add the frosting to a piping bag fit with a large round piping tip or alternatively you can add the frosting to a gallon sized zip top bag, cut the corner of the bag and use it to pipe the frosting onto the warm cookies in a spiral. Start in the center of the cookie and work your way out.
Sprinkle some extra cinnamon and sugar on top- serve warm!