Chocolate Whoopie Pies

Before you start

Whoopie pies are two mounded chocolate cakes with a thick white filling in between, associated with both Pennsylvania Dutch country and New England; their exact origin is disputed. The cake batter is made like a cake, with buttermilk and natural cocoa, then scooped onto a sheet so each half bakes into a soft, round dome.

Portion control makes or breaks them. Use a scoop so every half is the same size and they pair up neatly. Bake just until the tops spring back; a minute too long and they turn dry and crumbly instead of tender. The filling here is a marshmallow buttercream, combining butter, powdered sugar and marshmallow creme, which is fluffier and less greasy than a filling made only from shortening.

Ingredients

• Cakes260 g (2 cups plus 1 tbsp, spooned and leveled) all-purpose flour
• 45 g (½ cup) natural unsweetened cocoa powder
• 1¼ tsp baking soda
• ½ tsp fine salt
• 115 g (½ cup) unsalted butter — softened
• 200 g (1 cup packed) light brown sugar
• 1 large (about 50 g) egg — room temperature
• 1 tsp vanilla extract
• 240 ml (1 cup) buttermilk — room temperature
• Filling115 g (½ cup) unsalted butter — softened
• 120 g (1 cup) powdered sugar
• 200 g (7 oz jar) marshmallow creme
• 1 tsp vanilla extract
• Pinch fine salt

Method

1. Heat the oven to 175°C (350°F) and line two baking sheets with parchment. Sift the flour, cocoa, baking soda and salt together.
2. Beat 115 g butter and the brown sugar on medium speed for 3 minutes, until fluffy. Beat in the egg and vanilla.
3. On low speed, add the dry ingredients in three parts, alternating with the buttermilk in two parts, ending with the dry. Mix just until smooth; the batter will be thick enough to hold a soft peak.
4. Scoop level 3-tablespoon mounds of batter onto the sheets, 13 per sheet, about 5 cm (2 in) apart. Smooth any peaks with a damp finger.
5. Bake one sheet at a time for 10 to 12 minutes, until the cakes have domed and spring back when lightly pressed in the center. Cool on the sheet for 5 minutes, then move them to a rack to cool completely.
6. For the filling, beat 115 g butter until creamy. Add the powdered sugar and beat until fluffy, about 2 minutes. Add the marshmallow creme, vanilla and salt and beat on medium until smooth and light.
7. Pair the cakes by size. Pipe or spread about 2 heaping tablespoons of filling onto the flat side of half of them, leaving a small border. Top with the remaining cakes, flat side down, and press gently so the filling reaches the edge.

Tips for success

• Grease the scoop lightly or dip it in water between portions so the thick batter releases cleanly.
• Fill the pies at least 30 minutes before serving; the cakes soften slightly against the filling and hold together better.
• For neat edges, roll the exposed filling in mini chocolate chips or crushed cookies.

Substitutions

Buttermilk

Stir 1 tablespoon white vinegar into 240 ml whole milk and let it stand 5 minutes. The cakes will be slightly less tender but very close.

Natural cocoa

Dutch-process cocoa gives a darker, milder cake, but it does not react with baking soda, so replace the soda with 2 teaspoons baking powder.

Marshmallow creme filling

Use cream cheese frosting or Swiss meringue buttercream. Cream cheese fillings must be refrigerated.

Variations

Pumpkin whoopie pies

Leave out the cocoa, cut the buttermilk to 120 ml, and beat in 240 g pumpkin purée and 2 teaspoons pumpkin pie spice. Fill with cream cheese frosting and refrigerate the finished pies.

Peanut butter filling

Beat 120 g creamy peanut butter into the marshmallow filling and add a pinch more salt.

Troubleshooting

Cakes spread flat

The batter was too thin or the butter too warm. Weigh the flour, use room-temperature rather than warm ingredients, and chill the batter for 15 minutes if it looks loose.

Cakes are dry and crumbly

They were overbaked or the flour was over-measured. Pull them when the centers spring back, and weigh the flour.

Filling is runny and slides out

The butter was too soft or the kitchen is warm. Chill the filling for 15 minutes and beat again, or add a few tablespoons of powdered sugar.

Storage

Wrap each whoopie pie in plastic or store them in a single layer in an airtight container at room temperature for up to 2 days, or refrigerate for up to 5 days. Let chilled pies stand 15 minutes before eating. Freeze wrapped pies for up to 1 month.

Safety notes

Contains wheat, milk and egg. The raw batter contains uncooked egg and flour, so do not lick the bowl.