Mix Dry. In a bowl, whisk together the flour, cornstarch, baking powder, baking soda, and salt. Set aside.
Cream. In a large bowl, beat the butter, brown sugar, and granulated sugar until light and fluffy.
Add Wet. Mix in the eggs and vanilla extract until fully combined.
Combine. Add the dry ingredients and mix until a thick dough forms.
Fold. Fold in the milk chocolate chips and crushed Oreo cookies.
Shape. Scoop the dough into 2 tablespoon portions and place on a parchment lined baking sheet, spacing 2 to 3 inches apart. Press one mini Oreo into the center of each dough ball.
Bake. Bake at 350°F for about 10 minutes, until the edges are set.
Cool. Let rest on the baking sheet for at least 2 minutes before transferring to a wire rack to cool completely.
Notes
Setting Time. Allow cookies to sit on the baking sheet briefly after baking so they can finish setting before moving.
Make Ahead. Dough can be scooped and chilled in the refrigerator or freezer while baking additional trays.
Texture. Cookies will continue to cook slightly as they cool, keeping the centers soft.