Preheat the oven to 350 degrees F. and line an 8 x 8-inch square baking pan with parchment paper. Set aside.
In a medium-size bowl, whisk together the 2 cups all-purpose flour, 1 cup light brown sugar, ½ cup unsweetened cocoa powder, 1 teaspoon baking powder, and ½ teaspoon sea salt and set aside. In a separate small bowl whisk together the 1 cup oil, 1 cup water, ½ teaspoon peppermint extract, and 1 teaspoon vanilla extract until combined.
Add the oil mixture into the flour mixture and stir with a wooden spoon until fully combined, careful not to over mix. Stir just until all the ingredients come together.
Before you add the chocolate mint sandwich cookies to the brownie batter be sure to cut each cookie into quarters or place them in a Ziploc plastic bag and gently roll over the bag a few times with the rolling pin to break the cookies up just a little.
Using a spatula, gently fold in the quartered 20 mint creme filled chocolate sandwich cookies until evenly distributed. Add the brownie mixture into the prepared pan and place in the oven to bake for 25 to 30 minutes or until a tester comes out clean.
Carefully remove the brownies from the oven and allow them to cool completely in the pan on a rack prior to cutting into squares and serving. Enjoy!
Store any leftover brownies in cut up squares in an airtight container at room temperature up to 4 days.