Whoopie Pie

Directions

1. 1
   Preheat oven to 350°F.
2. 2
   For the cakes, whisk together flour, cocoa, baking soda, and salt in a bowl until combined.
3. 3
   Stir together buttermilk and vanilla in a small glass measuring cup.
4. 4
   Beat together the butter and brown sugar in the large bowl of a standing mixer for 3 minutes. Then, add egg, beating until combined well.
5. 5
   Reduce speed to low and alternately mix in flour mixture and buttermilk in batches, beginning and ending with flour. Be sure to scrape down the sides of the bowl from time to time.
6. 6
   The batter will be thick. Spoon sixteen 1/4-cup mounds of batter about 2 inches apart onto 2 Silpat-lined baking sheets. You'll have 8 per sheet. I used my new cookie dough scoop for this.
7. 7
   Bake in the upper and lower thirds of the oven. Switch the position of the sheets halfway through baking. Bake until tops are puffed and cakes spring back when touched, 11 to 13 minutes.
8. 8
   Transfer with a metal spatula to a rack to cool completely.
9. 9
   In the bowl of a standing mixer, beat together the filling ingredients on medium speed until smooth, about 3 minutes.
10. 10
    To assemble the pies, transfer the filling to a gallon-size Ziploc bag. Snip off one of the bottom corners. Pipe a tablespoon of filling onto the flat sides of half of the cakes. Top with the remaining cakes.
11. 11
    Enjoy with a cold class of milk.