In a small bowl, combine flour, baking soda, baking powder, salt & cornstarch. Whisk it together. Set aside.
In your mixer bowl, combine butter & sugars. Mix on medium speed for a few minutes until fluffy. Add eggs, one at a time, until each have been combined. Add vanilla. Beat mixture until smooth.
Turn mixer to low and begin to add flour mixture, about a half cup at a time, beating after each addition until it is all combined. Stir in chocolate chips.
Refrigerate dough for at least an hour.
Preheat oven to 350 degrees F. Line cookie sheet with parchment paper.
Scoop about a tablespoon of cookie dough into your palms and roll into a ball. Dip tops of cookie in sprinkles. Bake for 10-12 minutes.
After you remove cookies from oven, while they are still warm, place milk chocolate candy heart into the centers of each cookie. Let cookies cool for about a minute on the cookie sheet before moving to a wire rack to cool completely.