1.In a bowl of an electric mixer with paddle attachment, combine unsalted butter, sugar, and brown sugar and beat until well-combined and creamed (about 1-2 minutes on high speed).
2.Add egg and vanilla extract and mix again until well-combined. Plug in the waffle iron so it begins warming up.
3.In a separate bowl, whisk together flour, cornstarch, baking powder, baking soda, and salt. Gradually stir dry ingredients into wet with a spatula until completely combined.
4.Scoop approximately 2 Tablespoons of cookie dough and form into a ball. Break into 3 or 4 even pieces and place them evenly in the waffle iron (be careful, the iron will be very hot, do not touch the actual iron!).
5.Gently but firmly close the waffle iron and cook until cookie is golden brown (about 90 seconds). To remove the cookie, carefully tilt the waffle iron onto a cooling rack. Repeat with remaining cookie dough until all cookies have been cooked.
6.Meanwhile, whisk together maple syrup and 3/4 tablespoon melted butter. Gradually add powdered sugar until completely combined. Drizzle glaze over cookies.