Sift together 2 ¾ cups of all-purpose flour, 1 teaspoon of baking soda, 1 teaspoon of cornstarch, and ½ teaspoon of salt in a large mixing bowl. Set aside.

In an electric mixer, beat 1 cup of unsalted butter, ¾ cup of brown sugar, and ½ cup of granulated sugar on medium-high speed for about 2 minutes. Add 2 teaspoons of pure vanilla extract and mix well.

Add 2 large eggs, one at a time, mixing on low speed until fully blended.

Gradually mix the dry ingredients into the wet ingredients until just combined. Fold in 1 cup of semi-sweet chocolate chips and ½ cup of rainbow sprinkles.

Cover the dough with plastic wrap and refrigerate for 45 minutes.

Preheat the oven to 350°F (175°C) and line baking sheets with parchment paper.

Using a cookie scoop, portion out the dough and space six cookie balls on each baking sheet. Press additional sprinkles on top if desired.

Bake for 13-15 minutes until the edges are golden and centers appear slightly underbaked.

Let cookies cool on the pan for 4 minutes before transferring to a wire rack.