Lemon Cake Mix Whoopie Pies
These Lemon Cake Mix Whoopie Pies are soft, fluffy lemon cake sandwiches made from a boxed lemon cake mix and filled with creamy vanilla buttercream. They'rer an easy, pretty dessert perfect for spring and holidays.
Equipment
- 1 piping bag optional
- 1 star-shaped or plain round piping tip optional
Ingredients
Lemon Whoopie Pie Rounds
- 1 box lemon cake mix 15.25 oz
- 2 eggs
- 1/3 cup neutral oil
- 1/4 cup sour cream or plain Greek yogurt
- 1/4 cup milk
- 1 Tbsp lemon zest optional, but recommended
- 2 Tbsp cornstarch or flour helps the whoopie pie rounds keep their shape
- 1/2 tsp vanilla
Vanilla Filling
- 1 cup (2 sticks) unsalted butter softened
- 3 1/2 - 4 cups powdered sugar
- 1 tsp vanilla
- 2-3 Tbsp milk or heavy cream
Instructions
- Heat the oven to 350°F. Line baking sheets with parchment paper so the cakes release easily and keep their pretty shape.
- Zest a lemon
- In a large mixing bowl, add lemon cake mix, eggs, neutral oil, sour cream or Greek yogurt, milk, Lemon zest and vanilla extract. Stir until everything is combined and smooth. The batter should be thick and scoopable, more like cookie dough than runny cake batter.
- Use a 1 1/2 tablespoon cookie scoop or a heaping tablespoon to scoop mounds of batter onto the prepared baking sheets. Space them about 2 inches apart, because they will spread into cute little cake rounds while they bake.
- Bake for 8 to 10 minutes, until the tops spring back when lightly touched and the edges look set. Do not wait for browning, you want them soft and pale for that classic whoopie pie look. If they’re starting to brown, take them out of the oven immediately.
- Let the cakes cool on the baking sheet. When they’re completely cool and you’re ready to add the filling, carefully lift the whoopie pie rounds off the baking sheet. You may need a rubber spatula to gently pull them up.
- In a medium bowl, beat the softened butter with a hand mixer or stand mixer for about 1 minute until creamy. Add your powdered sugar a cup at a time, plus vanilla extract. Beat until light and fluffy.
- Add 1 tablespoon heavy cream or milk and mix again. If the filling is too thick, add another splash of cream or milk. If it is too thin, beat in more powdered sugar a little at a time.
- For a lemon vanilla twist, beat in more lemon zest (you'll need at least one other lemon's worth), then add lemon juice a few drops at a time until you like the flavor.
- Pair up your cooled lemon cake rounds by size so each sandwich looks neat and even.
- Transfer the filling to a piping bag with a star tip (I like the Wilton 1M tip) or zip-top bag with the corner snipped off. You can also just use a spoon or offset spatula.
- Pipe or spread a generous layer of filling onto the flat side of one cake. Then, top with the flat side of a second cake and gently press to spread the filling to the edges. Repeat with the remaining cakes and filling.
- Place the assembled whoopie pies in a single layer in an airtight container that’s lined with parchment paper or sprinkled with a bit of powdered sugar. Refrigerate for 3 to 4 days; let them come to room temperature before serving so the cakes are soft and the filling is creamy.