White Chocolate Lemon Raspberry Cake
My cousin always asks for a lemon-raspberry cake for her birthday and this is but one iteration – the two flavors are a natural pairing and there are many delectable ways to combine them. This variation is based upon “Woody’s Lemon Luxury Layer Cake” from Rose’s Heavenly Cakes by my good friend Rose Levy Beranbaum. I wanted to try a new-to-me lemony cake and Rose always has great ideas – and the photo of the cake in her book lured me in. The cake and frosting contain a good quantity of white chocolate. She likes Green & Black white chocolate because it is speckled with vanilla bean seeds as her cake showcases lemon and vanilla as the flavors. Since I wanted the lemon and raspberries to be the stars, I used Valrhona Ivoire white chocolate, which has no vanilla seeds, but has a wonderful rich flavor due to the cocoa butter content. I also used my own Lemon Curd recipe instead of hers. You will need a thermometer for this recipe. Note that there are several components: lemon curd, cake, custard base for buttercream, and the buttercream itself. The lemon curd can be made several days ahead and refrigerated. The cake can be made a day ahead as can the custard base and frosting. In fact, the whole cake can be assembled a day ahead of serving. Just make sure to bring it to room temperature before serving – I cannot stress this enough. If chilled the frosting will be hard, like a stick of chilled butter, and the flavors will be muted. The light creamy texture of the frosting and the subtle lemon and white chocolate flavors can only be showcased at room temperature.
Lemon Curd (in Basic Recipes section): Have this made and chilled, at least overnight
6 ounces white chocolate, such as Valrhona Ivoire, finely chopped
6 large egg yolks, at rom temperature
1 cup whole milk, divided into 1/3 cup and 2/3 cup, at room temperature
1 teaspoon vanilla extract
3 cups sifted cake flour
1 cup plus 2 tablespoons sugar
4 1/4 teaspoons baking powder
3/4 teaspoon salt
1 teaspoon lemon zest, made with a Microplane zester (very fine in texture)
9 tablespoons (1 stick plus 1 tablespoon) unsalted butter, at room temperature, cut into pieces
White Chocolate Custard Base:
10.6 ounces (300 grams) white chocolate, such as Valrhona Ivoire, finely chopped
1/2 cup plus 2 1/2 tablespoons (1 stick plus 2 1/2 tablespoons) unsalted butter, at room temperature, cut into pieces
4 large eggs, at room temperature
Additional Ingredients for Completing the White Chocolate Lemon Buttercream and Assembly:
1/2 cup plus 2 tablespoons (1 stick plus 2 tablespoons) unsalted butter, at room temperature, cut into pieces
2, 6 ounce containers of fresh raspberries (or about 3 1/2 cups total)
For the Cake: Position an oven rack in the middle of the oven. Preheat the oven to 350 degrees F. Coat two 9-inch x 2-inch cake pans with nonstick spray, line with parchment and spray parchment; set aside.
Melt the white chocolate in top of double boiler or in microwave; stir until smooth.
Whisk together egg yolks, 1/3 cup milk and vanilla in a small bowl and set aside.
In a bowl of a stand mixer fitted with a flat beater, mix the flour, sugar, baking powder, salt and lemon zest on low speed just until combined. Add the butter and 2/3 cup milk and mix on low-medium speed for about 30 seconds. Scrape down the bowl then mix for about 30 seconds more or until beginning to look smooth.
With mixer on low-medium speed, slowly add the egg mixture and beat for about 30 seconds. Scrape down the bowl then mix for about 30 seconds more or until smooth. Add the white chocolate and beat in until incorporated. Divide batter in the two prepared pans.
Bake for about 20 to 25 minutes or just until a toothpick inserted in the center shows a few moist crumbs when removed. Cool pans on racks for 10 minutes, unmold cakes directly onto racks, peel off parchment then cool completely. (Cakes may be made 1 day ahead. If not using right away, place cakes on 9-inch cardboard rounds to protect them, wrap well in plastic wrap and store at room temperature).
For the White Chocolate Custard Base: Melt the white chocolate and butter in top of a double boiler, making sure that the water doesnt not touch the top bowl/pot. Meanwhile whisk the eggs in a small bowl. Slowly whisk the beaten eggs into the melted white chocolate and continue to heat over the double boiler, whisking frequently, until the mixture reaches 140 degrees F. The mixture will have thickened and will be very smooth. Remove from the heat, scrape into a clean bowl and refrigerate until it registers between 60 and 70 degrees F. This might take up to an hour; whisk it occasionally to release heat.
For Completing the White Chocolate Lemon Buttercream: Beat the butter until smooth and creamy in bowl of a stand mixer fitted with balloon whip attachment. Add the white chocolate custard base in three batches, beating well after each addition and scraping down the bowl. Whip on high speed until stiff peaks form. Check temperature; buttercream should be no higher than 70 degrees F. If it is warmer, chill in an ice bath and beat again until smooth once chilled. Beat in 1/3 cup of Lemon Curd until smooth.
Assembly: Plan on assembling the cake a day ahead or at least 6 hours ahead. The time allows the flavors and textures to meld and develop.
Cut each cake in half so that you have four even layers. Place one layer on a 9-inch cardboard round or simply place directly on your serving platter. Spread about one-third of the remaining lemon curd on top of the cake; top with another cake layer. Spread about 3/4-cup of the buttercream on top of that layer then using one container of raspberries, nestle the berries upright, side by side in the buttercream all over the cake layer. Top with another cake layer, half of the remaining lemon curd and then the last cake layer. Frost the top and sides with the buttercream and chill the cake for 30 minutes to set buttercream. Spread remaining lemon curd on top of cake using a small offset spatula leaving a half-inch border around the edges. Using the last container of berries, pick out the most similarly sized ones and place them upright in a ring around the edge of the cake; they should fill the empty space between the lemon curd and the edge. Refrigerate the cake up to one day. Make sure to bring to room temperature before serving (which could take several hours depending on ambient temperature).