Start by preheating your oven to 400°F and lining two baking sheets with parchment paper. While the oven heats, crush your peppermint candy and Oreos into small pieces—I like to use a food processor for the Oreos so they break down evenly, and I crush the peppermint by hand in a bag so I can control the size better and get some larger pieces for texture. Measure out all your dry ingredients (flour, cornstarch, baking soda, and salt) into a small bowl and whisk them together to distribute the leavening evenly.

In a stand mixer (or with a hand mixer), combine the softened butter, packed brown sugar, and granulated sugar. Beat on medium speed for 3-4 minutes until the mixture is light, fluffy, and pale in color. This creaming process incorporates air into the dough, which helps the cookies rise slightly and creates a better texture.

With the mixer still running on medium speed, add the room-temperature eggs one at a time, allowing each egg to fully incorporate before adding the next. Once both eggs are mixed in, add the vanilla extract and beat until everything is well combined and homogeneous.

Reduce mixer speed to low and gradually add the dry ingredient mixture from Step 1 (flour, cornstarch, baking soda, and salt). Mix just until the dough comes together and no dry flour streaks remain—be careful not to overmix, as this can develop gluten and make the cookies tough.

Switch to a rubber spatula and gently fold in the crushed peppermint candy, crushed Oreos, and both chocolate chips until evenly distributed throughout the dough. I like to do this by hand because it gives me better control and prevents overmixing the dough.

Using a cookie scoop or spoon, drop rounded portions of dough onto the prepared baking sheets, spacing them about 2 inches apart. Bake for 10-12 minutes until the edges are golden brown but the centers still look slightly underdone—they will continue to cook as they cool. The cookies should look just set when you pull them from the oven.

Allow the cookies to cool on the baking sheet for 5 minutes, which lets them firm up enough to handle without falling apart. Transfer them to a wire cooling rack to cool completely. Once cooled, they’re ready to serve or store in an airtight container.