2 cups all-purpose flour
1/2 cup Dutch-process cocoa powder
1-1/4 teaspoons baking soda
1 teaspoon salt
1 cup well-shaken buttermilk
1 teaspoon vanilla
1 stick butter, softened
1 cup packed brown sugar
1 extra large egg
Preheat oven to 350°F. Whisk together flour, cocoa, baking soda, and salt in a bowl until combined. Stir together buttermilk and vanilla in a small bowl.
Beat together butter and brown sugar in a large bowl with an electric mixer at medium-high speed until pale and fluffy, about 3 minutes in a standing mixer or 5 minutes with a handheld, then add egg, beating until combined well. Reduce speed to low and alternately mix in flour mixture and buttermilk in batches, beginning and ending with flour, scraping down side of bowl occasionally, and mixing until smooth.
Spoon 1/4-cup mounds of batter about 2 inches apart onto 2 buttered large baking sheets. Bake in upper and lower thirds of oven, switching position of sheets halfway through baking, until tops are puffed and cakes spring back when touched, 11 to 13 minutes. Transfer with a metal spatula to a rack to cool completely.
Marshmallow Ice Cream
2 cups half and half
1 10-oz. bag of large marshmallows
2 cups heavy cream
2 tablespoons vanilla
In a large pot, combine half and half with marshmallows. Cook over medium heat, stirring frequently until marshmallows have completely melted. Remove from heat and let cool briefly. Then place in fridge to cool for 20-30 more minutes, until chilled and slightly thickened.
In the meantime, whip heavy cream until you have soft peaks. Fold into cooled marshmallow mixture and add vanilla extract. Stir until everything is combined. Place in ice cream maker and follow manufacturer’s directions for making ice cream.
Spread a rounded tablespoon filling on flat sides of half of cakes and top with remaining cakes. You will have extra ice cream left after you make the Whoopie Pie Ice Cream Sandwiches - so enjoy or freeze for later.