Preheat oven to 350 degrees.
Grease (or line with parchment paper) a 12x6 or 9x9 baking dish.
Prepare the brownie batter according to package instructions.
Arrange half of the waffle cookies on the bottom of the prepared baking dish.
Arrange the chopped Samoas evenly on top of the waffle cookies.
Top with the brownie batter.
Arrange the remaining waffle cookies on top of the batter.
Bake for 25 - 27 minutes.
Remove from oven and allow to cool for 10 minutes. Dust with powdered sugar (if using) before serving.