This was a favorite treat when we lived in Whittier, Alaska running the cruise ship operations for Princess Cruises.  A small coffee shop opened up on the waterfront and we found this on their menu and they kindly shared the recipe with us!

Ingredients:

Brownie Mix (or Homemade brownie recipe if you have THAT kind of time!)
Mini Marshmallows
Nuts (we like Macadamia but Walnuts are good too)

Preparation:

Mix together and bake!