Lyndsay Sung’s Buttercream Flower Garden Holy Sheet Cake

I made a version of this beautiful buttercream flower–piped “Holy Sheet Cake” for Cherry Bombe’s Jubilee in Seattle back in late 2019 with a vanilla milk–soaked vanilla cake with a raspberry jam layer, topped with vanilla Swiss meringue buttercream flowers, drop stars, and leaves, and finished with fresh raspberries. I named it The Holy Sheet Cake at the time, and getting it frosted, piped, sliced, and individually plated for 200+ guests was truly a holy sheet miracle—I felt like I was living my own Top Chef elimination challenge. With the help of some awesome assistants, the cakes were served and I met so many wonderful folks and had the best day. I love this color blast of a cake—it’s an homage to, and a celebration of, all the brilliant, dynamic, and inspiring women in food I have met through Cherry Bombe and their community-building Jubilee conferences.

Makes one 9x13 inch sheet cake

Ingredients

for the vanilla Sheet Cake

1 cup (250 milliliters) soy milk
½ cup (125 grams) sour cream
5 tablespoons (75 milliliters) aquafaba
1 tablespoon pure vanilla extract
3 cups (390 grams) cake flour
1½ cups (300 grams) granulated white sugar
1 teaspoon baking powder
¾ teaspoon baking soda
¾ teaspoon fine sea salt
1 cup (224 grams) unsalted plant-based butter, room temperature

for the Vanilla Milk Soak

1 cup (250 milliliters) soy milk
3 tablespoons granulated white sugar
1 teaspoon pure vanilla extract
Pinch of salt

for the Frosting

Raspberry jam (page 141 in Lyndsay’s book or use your favorite store-bought one)
1 recipe Vanilla Swiss Meringue Buttercream (page 130 in Lyndsay’s book or use your favorite recipe)
4 gel colors of your choice
2 dozen fresh raspberries

Make the cake: Preheat the oven to 350°F (175°C). Prepare a 9×13-inch rectangular cake pan by spritzing it with vegetable oil and lining with a parchment paper rectangle cut to size, and then spritzing again with oil, to prevent sticking.

In a large bowl, using a balloon whisk, vigorously whisk the soy milk, sour cream, aquafaba, and vanilla extract together until combined and frothy.

In the bowl of a stand mixer fitted with the paddle attachment, mix together the cake flour, sugar, baking powder, baking soda, and salt until combined.

With the mixer on low speed, add the butter, 1-inch pieces at a time (I just use a butter knife to slice off pieces from the brick of butter right into the bowl). The mixture should clump up and look as if there are some coarse sand–like pieces in there.

With the mixer still on low, pour in half of the whipped milk mixture, mixing for about 15 seconds to incorporate. Pour in the remaining milk mixture and mix until a smooth batter forms, about 30 seconds. To avoid overmixing, if needed, finish the batter by hand using a rubber spatula for a few more turns until completely incorporated.

Bake the cake: Pour the batter into the prepared cake pan, tapping the pan on the counter a few times to reduce any air bubbles. Smooth the batter with an offset spatula, if needed. Bake for 30 to 34 minutes, until the cake is lightly browned on the top and edges, and a toothpick inserted into the center comes out with only moist crumbs.

Let the cake cool completely in its pan set on top of a wire rack.

Make the vanilla milk soak: In a small saucepan set over medium heat, combine the soy milk, sugar, vanilla extract, and salt, stirring until the sugar has dissolved completely. Remove from the heat and let cool completely.

Assemble the cake: The ease of sheet cakes is that you can serve them right in the pan they were baked in! But if you want to serve on a cake board, see the note below.

Using a serrated bread knife, trim off any dome from the cake, keeping the trimmings for a snack. Using a pastry brush or teaspoon, generously brush the vanilla milk soak all over the cake, using enough to impart flavor but not so much that the cake becomes mushy.

Apply a thin layer of jam on the entire cake. Using a rubber spatula, dollop enough vanilla Swiss meringue buttercream to the center of the cake to make a thin but substantial layer, then carefully spread the buttercream to the edges of the cake. Don’t worry if it gets a bit mingled up with the jam, as the whole cake will be covered in colored buttercream piping!

Decorate the cake: Dot the entire cake in an even pattern with the raspberries, pressing them lightly into the buttercream.

Divide the remaining buttercream between four bowls. Tint each bowl with your favorite gel colors—I used fuchsia pink, turquoise, avocado green, and Wedgwood blue for the cake in this photo. Fit four piping bags each with a different piping tip (I used Wilton 4B for the pink and blue, Wilton 1M for the turquoise, and Wilton 70 for the avocado green), then fill each with a different color of buttercream, reserving the leaf tip for the avocado green. Pipe an assortment of different-sized drop stars and rosettes all over the cake, adding piped leaves to fill in any holes.

For neat and tidy slices, chill the cake for 30 minutes before slicing, wiping your knife clean between cuts.

This cake will taste freshest eaten within a day of making it, but can be stored in the fridge, covered, for up to 3 days.

Note: To unmold a sheet cake from the cake pan, run an offset spatula around the edges of the cooled cake. Place a large cutting board directly on top of the cake pan. Carefully but deftly invert the cake onto the cutting board, then peel off the parchment paper. Place your cake board or a large platter on the bottom of the cake, then turn the cake right side up.

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Open BookCatherine BakerSeptember 14, 2023Recipes, open book