Prepare the Dry Ingredients: In a medium mixing bowl, whisk together the flour, cornstarch, baking soda, and salt. Set aside.

Mix Wet Ingredients: In a large bowl, cream together softened butter, granulated sugar, and brown sugar until smooth. Mix in vanilla extract and egg yolks.

Combine Mixtures: Gradually add dry mixture to wet ingredients, mixing until just combined. Fold in mini chocolate chips.

Shape and Chill Dough: Divide the dough into two logs, wrap in plastic, and chill for at least 1 hour.

Slice and Bake: Preheat oven to 350°F. Slice dough into rounds, arrange on a baking sheet, and bake for 5 to 7 minutes.

Cool and Serve: Allow cookies to cool on the baking sheet for 5 minutes, then transfer to a wire rack.