Despite some questionable reviews that surfaced on their site post purchase, the brownie mix/PAM combo worked perfectly for us. I filled it with Whoopie pie filling and it was amazing. We're going to recreate the whole thing again later this week :).
Whoopie Pie Filling
(traditional amish recipe found via ye olde google)
1 cup solid vegetable shortening
1 1/2 cups powdered sugar
2 cups Marshmallow Fluff
1 1/2 teaspoons vanilla extract