First whisk together the egg, egg yolk, sugar, brown sugar, and vanilla until light and fluffy.
Stream the melted butter and chocolate into the mixing bowl, whisking until just combined.
Fold in the dry ingredients and the chopped andes mints.
Spread the brownie batter into a square baking pan. Bake at 350 for 20 minutes, then cool.
Drizzle with chocolate and sprinkle with more chopped mints and enjoy!