Using a large mixing bowl, cream the butter, granulated sugar, and brown sugar. Add the vanilla, then the eggs. Cream until light.
1 cup butter, 1 cup brown sugar, ¼ cup granulated sugar, 2 medium eggs, 1½ teaspoon vanilla extract
In a medium mixing bowl, combine the flour, cornstarch, baking powder, baking soda, cinnamon, and salt. Use a whisk and distribute the cinnamon evenly. Add the blended dry ingredients gradually to the creamed butter & sugar bowl, using a hand mixer.
2¾ cups flour, 1 tablespoon cornstarch, 1 teaspoon baking powder, ½ teaspoon baking soda, 2 teaspoon cinnamon, ¼ teaspoon salt
Divide the cookie dough into 12 balls, about ¼ cup per cookie dough ball. Roll each ball into the reserved bowl of cinnamon sugar mixture.
Place each sugar coated cookie dough ball on a prepared rimmed cookie sheet, about 2" apart, 6 per cookie sheet. Save the left over cinnamon sugar for later.
Bake in the prepared over for 10 minutes. Remove from oven, let cool for 5 minutes and then transfer to a cooling rack. Let cool completely before frosting.