Preheat oven to 375 degrees F, line a baking sheet with parchment paper or a silicone baking liner and set aside

In a medium bowl combine flour, cornstarch, baking soda, baking powder, cinnamon and salt. Mix it up and set aside.

In a large bowl using electric beaters or in a stand mixer cream together cold butter and both sugars. Cream this together until uniform and no lumps of butter remain (~2 minutes)

Add egg, egg yolk, and vanilla to the butter mixture and mix until just combined.

Slowly add the flour mixture to the wet ingredients and mix until combined and uniform. (If there will be any delay in your cookie baking, place dough in the fridge!)

In a small bowl combine the cinnamon sugar coating.

Take ~2 tbsp of the cookie dough, roll it into a ball and then roll it in the 

cinnamon sugar. Place your ball onto the cookie sheet (Don’t press it down- leave it in a ball!) and then repeat with remaining dough.

Bake cookies for 9 minutes, remove from oven and allow to cool fully.

Enjoy!