Make the brownies: Melt half a stick of butter in a small saucepan. Remove from heat and stir in cocoa and sugar. Stir in flour, salt, vanilla, and egg until combined. Pour into a greased loaf pan and bake 15-20 minutes, or until a knife inserted into the middle removes clean or with minimal gooey chocolate. Cool completely.
Filling: Beat all ingredients together until smooth. Spread over cooled brownies and refrigerate one hour.
Ganache: Heat cream until it almost reaches a boil. Pour over chocolate and sprinkle with salt. Allow to rest thirty seconds and then stir until smooth. Spread over frosting. Top with cookie crumbles.
Note: If you have any leftover mint filling, stuff Oreo cookies with it. It's a phenomenally easy treat that kids and adults will love!
Find it online: https://livelaughrowe.com/thin-mint-brownies/