Lemon Poppyseed Birthday Cake

It's Ballerina Farm's 9th birthday! This year, we celebrated with a giant 8-foot cake that stretched along the entire pastry case at our Midway store. The taste was just as impressive as the size—a plush, citrusy lemon cake with no shortage of poppy seeds. To make this classic sponge cake, simply whip whole eggs, sugar, and lemon zest until tripled in volume, then add flour, lemon juice, butter, and oil. The flavor is divine, and the texture tender and moist. You can fill and decorate this cake as simply as you’d like, or go all-out and assemble it just like we do in the kitchen: with layers of white chocolate mascarpone mousse and lemon curd, frosted with our classic buttercream. 

Yields: 12 slices | Prep Time: 1 hour 50 minutes | Bake Time: 25 minutes | Rest Time: 2 hours

Ingredients

Lemon Poppyseed Sponge Cake

• 1 ¼ cups (250 grams) granulated cane sugar
• 4 tablespoons (25 grams) lemon zest, about 5 to 6 lemons
• 3 large eggs
• 2 egg yolks
• 2 cups (240 grams) Ballerina Farm High Protein Flour
• 2 teaspoons baking powder
• ¼ teaspoon baking soda
• 1 ¼ teaspoon kosher salt
• 2 tablespoons (18 grams) poppy seeds
• 1 cup (227 grams) whole milk
• ½ cup (113 grams) unsalted butter
• ¼ cup (50 grams) avocado oil
• ¼ cup plus 1 tablespoon (70 grams) lemon juice, about 3 to 4 lemons

Filling & Frosting

• 2 ½ cups White Chocolate Mascarpone Mousse 
• 2 cups Ballerina Farm Lemon Curd
• 3 ½ cups Swiss Meringue Buttercream
• Poppy seeds and edible flowers, for decorating (optional)

DIRECTIONS

Make the Cake

1. Preheat the oven to 350 degrees Fahrenheit. Line the bottom of an 18 x 13-inch sheet pan with parchment paper.
2. Add the sugar and lemon zest to the bowl of a stand mixer, then rub together with your fingers until the sugar is the texture of wet sand. Focus on eliminating any clusters of zest. 
3. Before cracking the eggs, place them in a bowl under hot running water for 2 to 3 minutes to warm them just above room temperature. This will help them hold volume as they whip. Crack the eggs, then add the whole eggs and egg yolks to the sugar. Using the whisk attachment and whip the eggs and sugar together until the eggs are pale and have tripled in volume. This will take about 6 to 8 minutes. 
4. In a separate bowl, sift together the flour, baking powder, and baking soda. Add the salt and poppy seeds, then set aside. 
5. In a saucepan (on the stove) or glass measuring cup (in the microwave), heat the butter, milk, and oil until the butter is just melted. Let the mixture cool slightly (it’s okay if it’s still warm), then add the lemon juice and briefly whisk to combine. 
6. Add half of the flour mixture to the whipped eggs and mix on low speed for about 10 turns of the whisk, or until the flour is nearly incorporated. While the mixer is still running, slowly stream in about half of the milk mixture until barely combined. Turn off the mixer, add the remaining flour, mix on low speed for another 10 turns of the whisk or until the flour is nearly incorporated. With the mixer still running, slowly stream in the remaining milk mixture until barely combined. 
7. Scrape the whisk and sides of the bowl, then gently fold the batter a few times to incorporate any dense pieces of batter. 
8. Transfer the batter to the pan and bake for 20 to 25 minutes, or until the center springs back when gently pressed. This cake only rises about ¼-inch (at most) during baking, so you can fill the cake pan quite full!
9. Let the cake cool completely in the pan, about 1 hour. Carefully remove it from the pan. If you have a cutting board or cooling rack large enough, place it on top of the cake, then hold it steady as you flip the pan over to release the cake from the pan.
10. Slice the cake in half lengthwise, then slice it in half crosswise to yield 4 rectangles. 

Fill & Frost the Cake

11. Assemble the cake. Place one slab of cake on a platter or cake stand. Add the mousse to a piping bag with a large, round tip and pipe a border around the edges of the cake. 
12. Add about ½ cup of lemon curd to the center of the cake, spreading it evenly between the borders of mousse. Place another slab of cake on top, then repeat piping the mousse and adding another ½ cup of lemon curd. Top with another slab of cake, then repeat this process a final time, adding the last slab of cake on top. 
13. Use an offset spatula to spread a very thin layer of buttercream over the top and sides of the cake to create a crumb coat. Cover the cake and refrigerate for about 1 hour, then uncover the cake and continue frosting the cake until evenly coated in a layer of buttercream. 
14. Using a large ribbon piping tip, pipe ribbons of buttercream around the top edges of the cake to create a border. Fill the center with a thin layer of lemon curd, then sprinkle with poppy seeds and edible flowers (if using). Cover and refrigerate until ready to serve.