Preheat the oven to 350°F (175°C). Butter the bottom and sides of an 8-inch square metal baking pan. Line the pan with a sheet of parchment paper, allowing it to overhang on two opposite sides for easy removal. Lightly butter the parchment paper as well.

In a small saucepan over medium heat, melt the butter. Once melted, add the granulated sugar and whisk continuously. Bring the mixture to a gentle boil and continue to whisk for 1 minute. Remove from heat and allow to cool for 5 minutes.

In the bowl of a stand mixer fitted with the paddle attachment (or using a hand mixer), combine the softened cream cheese, confectioners’ sugar, 1 teaspoon of vanilla extract, and the peppermint extract. Beat until smooth and fully incorporated, approximately 1 minute. Set aside.

In a medium mixing bowl, sift together the flour, cocoa powder, and salt. Whisk to ensure the dry ingredients are evenly distributed.

In a large mixing bowl, whisk the eggs until fully blended. Gradually add the slightly cooled butter-sugar mixture and whisk until well combined.

Stir the flour mixture into the egg and butter mixture until just combined. Gently fold in the chopped Thin Mint cookies.

Pour half of the brownie batter into the prepared baking pan and spread evenly. Add the cream cheese mixture on top of the brownie layer and gently spread to cover. Spoon the remaining brownie batter in dollops over the cheesecake layer. Using a knife or spatula, swirl the two mixtures together for a marbled effect.

Bake for 24 to 28 minutes, or until the cheesecake layer is set and a knife inserted into the center comes out mostly clean. The edges should appear lightly browned.

Allow the brownies to cool completely in the pan on a wire rack. Once cooled, lift them out using the parchment paper overhang. Slice and serve as desired.