Preheat your oven to 375°F and prepare your baking sheets with parchment paper. In a stand mixer, combine room temperature unsalted butter, granulated sugar, and brown sugar. Beat on medium-high speed for about 5 minutes until the mixture is light and fluffy.

Add your large eggs one at a time, mixing well after each addition, then pour in the vanilla extract and mix for an additional minute.

In a separate bowl, sift together all-purpose flour, cornstarch, baking soda, baking powder, and salt. Gradually add this dry mixture to the wet ingredients in your stand mixer on low speed until just combined.

Gently fold in the semi-sweet chocolate chips and Easter sprinkles using a spatula.

Using a 4oz cookie scoop, portion out the dough, flatten each round slightly, place one Peep marshmallow in the center, and wrap the dough around the marshmallow.

Chill the formed cookie dough balls in the refrigerator for at least 2 hours, or up to 48 hours.

Place four stuffed cookie dough balls on each prepared baking sheet and bake for 14-16 minutes until the edges are golden brown and the centers look slightly underbaked.

Let the cookies sit for 20-30 minutes on the tray to help them set perfectly before transferring to a wire rack to finish cooling.