Using a 1 tablespoon measuring spoon, scoop out 7 equally sized rounded tablespoons of Nutella onto a plastic wrapped plate or baking sheet and freeze for 30 minutes or until solid.
Make the cookie dough
Preheat the oven to 350F then line a baking sheet with parchement paper and set aside.
Cream the butter, granulated sugar, and brown sugar together until light and creamy. Add in the egg, vanilla extract, and mix until smooth.
Gently mix in the flour, corn starch, cream of tartar, baking powder, baking soda, cinnamon, & salt until the flour mixture disappears.
Scoop out equally sized cookie dough balls, gently flatten them n between the palm of your hand and place the fozen Nutella in the center. Gently fold the cookie dough over it. Roll the dough in between the palm of your hand, then roll in the cinnamon-sugar mixture, place on the baking sheet. (Read make the cinnamon-sugar mixture below to see how to make it)
Bake the cookies in the preheated oven for 12 minutes then let the cookies sit on the baking sheet until fully cool.
Make the cinnamon sugar mixture
Mix the 2 tablespoons of granulated sugar with 1/4 teaspoon of cinnamon in a shallow bowl.
Roll the cookie dough balls in this cinnamon sugar before baking.
Notes
How to store Crumbl hazelnut churro cookies?
You can store these cookies in an airtight container at room temperature for up to 5 days.