Preheat oven to 350°F. Grease and line a 9″x9″ pan with parchment paper and set aside.
In a bowl set over boiling water, combine butter and two sugars. Melt and stir with a whisk until the sugars are completely combined with the butter. This can be done in the microwave as well on 30 second intervals. You are looking for the mixture to be glossy when mixed.
Allow this mixture to cool slightly, and then add in the eggs one at a time. Make sure you are whisking in between each addition. Whisk until the mixture lightens in color slightly.
Add in the cocoa powder, salt, and peppermint extract. Fold in flour until just combined.
Lastly, fold in about 3/4 of the Mint Oreo cookie pieces.
Pour mixture into prepared baking pan and top with the remaining 1/4 of the crushed Oreos. Then bake for roughly 45-50 minutes, testing the doneness by inserting a knife or toothpick into the center of the brownies beginning at around 40 minutes. It will be slightly longer or quicker depending on your oven. Cool and ENJOY!