Cream the Butter and Sugar: In a stand mixer, beat 1 cup of cold cubed unsalted butter with 1 cup of brown sugar for 2-3 minutes. Add eggs one at a time, beating well after each addition. Mix in the vanilla extract.

Combine Dry Ingredients: In a separate bowl, combine 3 cups of flour, 1 teaspoon of cornstarch, 1 teaspoon of baking soda, and 1 teaspoon of salt. Fold this mixture into the wet ingredients until a dough forms.

Add Festive Mix-Ins: Incorporate 1 1/2 cups of chopped Oreo cookies, 1 1/2 cups of M&Ms, and 1/3 cup of festive sprinkles into the dough. Mix well.

Chill and Bake: Refrigerate the cookie dough for 30 minutes. Roll into large cookie dough balls (yielding approximately 12 cookies). Bake at 415°F for 10-12 minutes.

Rest and Enjoy: Allow the giant cookies to rest for 30 minutes before indulging in their soft and gooey goodness.