Step 1

Preheat oven to 400 degrees (if making cookies smaller than 6 ounces, preheat oven to 385 degrees).

Step 2

In a large mixing bowl, cream together butter, brown sugar, and sugar for 4 minutes until light and fluffy. Scrape the sides of the bowl halfway through. Add eggs and vanilla and mix for 1 minute longer.

Step 3

Fold in cocoa powder, flour, cornstarch, baking soda, and salt. Fold in chocolate chips and peppermint baking chips.

Step 4

Roll into large 6-ounce balls. You can make them smaller into 3-ounce, 4-ounce, or 5-ounce balls. Place on a light-colored baking sheet. If you want them to be slightly thinner, press down on the cookie dough ball before baking.

Step 5

Bake for about 8-11 minutes, depending on how large the cookies are. These cookies will be slightly underbaked and will continue to bake on the baking sheet once the cookies are removed from the oven. Let sit for at least 10 minutes to allow time for the cookies to set-up.