These incredible chocolate whoopie pies are made with two soft and fluffy chocolate cake rounds and a layer of creamy vanilla frosting sandwiched in between.
Preheat oven to 350F and line two baking sheets with parchment paper.
In a medium bowl, whisk together the flour, cocoa powder, baking soda and salt. Set aside.
2 cups (250g) all-purpose flour, 1/2 cup (60g) unsweetened cocoa powder, 1 1/4 tsp. baking soda, 1/2 tsp. salt
In the bowl of an electric mixer fitted with the paddle attachment, cream butter and sugar until light and fluffy. Add egg and vanilla. Beat until well combined.
1/2 cup (114g) unsalted butter, 1 cup (200g) granulated sugar, 1 large egg, 1 tsp. vanilla extract
Gradually add in the milk, scraping the bottom of the bowl as needed. The batter might curdle, but don't worry, it will come together when you add the dry ingredients.
1 cup (250ml) milk
Slowly add dry ingredients. Mix until just combined.
Using a 1-oz cookie or ice cream scoop, drop the batter onto the prepared baking pan 2" apart. Bake for 10-12 minutes or until a toothpick inserted into the center comes out clean. Let cool completely before frosting.
Filling
In the bowl of an electric mixer fitted with the paddle attachment, cream butter until smooth and creamy. Add in the vanilla, one cup of powdered sugar, and one tbsp of milk. Mix well. Add the remaining powdered sugar, one cup at a time, alternating with 1 tbsp of milk at a time. Add in the last tbsp of milk if needed for the desired consistency.
Transfer buttercream to a disposable pastry bag and snip the end. When cookies have cooled completely, pipe the buttercream onto the flat side of half the cookies. Sandwich with remaining cookies, pressing down slightly so that the filling spreads to the edge of the cookies.
Notes
Leftovers can be stored in an airtight container lined with wax paper at room temperature for 2-3 days and in the fridge for up to 5 days. Bring to room temperature before serving.To Freeze - Individually wrap the whoopie pies and store them in the freezer for up to 3 months. Thaw overnight on the counter before serving.