To begin, preheat your oven to 350 and line two pans with parchment paper (or spray with non-stick spray).

In a small mixing bowl, add your dry ingredients (flour, cornstarch, baking soda and salt) and mix them together.

In a large mixing bowl, add your butter and white sugar and beat them together with a hand mixer for a couple minutes till they are nice and creamy. Add your vanilla and egg, and lightly beat them into the mixture.

Pour your dry ingredients into your large bowl of wet ingredients, and stir them together till you have a thick cookie dough batter. Add your sprinkles and gently fold them into your batter.

Using a small cookie dough scoop, scoop your cookie dough and place the cookie dough balls onto your pans, evenly spaced apart with no more than 12 cookies per pan. If you would like, you can gently press a few sprinkles into the tops of each cookie for extra sprinkle fun.

Bake in the oven for 9-11 minutes, or till the edges of the cookies have set but the center still looks a touch underdone. It will cook through as it cools, and give you an ultra soft cookie.

Let cool for at least 15 minutes, then move them to a cooling rack till they are entirely cool. Devour!