Cream together softened butter, granulated sugar, and light brown sugar
Beat in eggs and vanilla extract
Combine cake flour, cornstarch, baking powder, baking soda, and salt
Mix dry ingredients into wet ingredients to form cookie dough
Prepare filling by mixing softened butter, light brown sugar, vanilla extract, all-purpose flour, ground cinnamon, and salt
Prepare icing by combining powdered sugar, dark brown sugar, milk, light corn syrup, vanilla extract, and ground cinnamon
Assemble cookies by placing filling between two cookie bases
Top cookies with brown sugar cinnamon icing
