Giant Ganache-Topped Whoopie Pie Great recipe! I added about 3 Tbsp Peanut Butter to the filling and it was awesome!! If not, next time I think I might just use marshmallow cream for the filling. I also didn't like the way the ganache came out. So, I made my own with a jar of Smuchers Hot Fudge, I thinned it out with a little pet milk, warmed it up, and poured it over the cake. This will be my new ganache recipe from now on!