Combine butter and sugars in a large mixing bowl and use an electric mixer to beat until light, fluffy, and well-creamed.

Add eggs and vanilla extract and stir again until thoroughly combined. Set aside.

In a separate mixing bowl whisk together flour, cornstarch, baking powder, baking soda, and salt.

Gradually add dry ingredients to wet, stirring until completely combined.

Cover dough tightly with plastic wrap and transfer to the refrigerator to chill for 30-60 minutes.

While the dough chills, prepare the filling.

In a mixing bowl, combine butter, sugar, and vanilla, then stir or beat with an electric mixer until smooth and creamy.

Sprinkle flour, cinnamon, and salt over the mixture and stir until well-combined.

Remove chilled cookie dough from the refrigerator and scoop by ¼ cup. Form one half into a nest and scoop filling into the center. Seal with the other half of cookie dough.

Place cookie dough on a baking sheet and freeze for 15-30 minutes.

Preheat the oven to 375F and line a baking sheet with parchment paper.

Bake for 14 minutes, until edges are golden brown. Allow to cool completely before icing.

In a small bowl, combine powdered sugar, brown sugar, milk, corn syrup, vanilla extract, and cinnamon. Whisk until smooth.

Immediately drizzle over cooled cookies and allow to set before enjoying.