Preheat oven to 350°F. Line a 9x13 inch baking pan with parchment paper.

In a large bowl, mix melted butter, granulated sugar, and cocoa powder until combined. Add eggs and vanilla extract, mixing well.

Stir in flour and salt until the batter is smooth. Pour into the prepared baking pan.

Bake for 20-25 minutes or until a toothpick inserted in the center comes out mostly clean. Allow to cool completely in the pan.

For the mint layer, beat together powdered sugar, softened butter, peppermint extract, and milk until smooth. Spread evenly over cooled brownies.

For the chocolate topping, melt chocolate chips and butter together in the microwave or over a double boiler until smooth. Pour over the mint layer.

Refrigerate for at least 1 hour to set the chocolate. Cut into squares before serving.