Lemon–White Chocolate Cheesecake Mousse Cake

If it’s too hard to choose between cake and cheesecake, make this and have both! This special occasion cake combines a light, airy lemon sponge with a rich white chocolate cheesecake mousse filling. For best results, use pure white chocolate for the filling.

MAKES: one 8-inch cake; 8 to 12 servings

PREP TIME: 1 hour

COOKING TIME: about 30 minutes

CHILLING TIME: at least 4 hours, 10 minutes

INGREDIENTS:

LEMON CAKE

• 3 ¼ cups cake-and-pastry flour, sifted
• 1 Tbsp baking powder
• 1 Tbsp finely grated lemon zest (1 to 2 lemons)
• 1 ½ tsp fine sea salt
• 7 large eggs
• 1 ¾ cups granulated sugar
• 3 Tbsp freshly squeezed lemon juice (1 to 2 lemons)
• 2 tsp vanilla extract
• 1 cup unsalted butter, melted and cooled

WHITE CHOCOLATE CHEESECAKE MOUSSE

• ¼ cup freshly squeezed lemon juice, chilled (about 2 lemons)
• 2 ½ tsp unflavoured powdered gelatin
• 1 cup whipping cream (35%)
• ⅓ cup plus 1 Tbsp white chocolate chips or finely chopped white chocolate
• 1 pkg (8 oz/250 g) brick-style cream cheese, at room temperature
• 1 ½ tsp vanilla extract
• 1 large egg white
• Pinch of fine sea salt
• ½ cup granulated sugar

TO ASSEMBLE

• Simple Syrup (made with granulated sugar and still warm)
• ½ tsp lemon extract
• 1 cup whipping cream (35%), chilled
• 2 Tbsp instant-dissolving sugar
• Finely grated lemon zest and thinly sliced lemon for garnish

INSTRUCTIONS:

1. Preheat the oven to 350°F. Grease the base of two 8-inch round baking pans, then line the base of each pan with parchment paper.
2. For the lemon cake, whisk together the flour, baking powder, lemon zest and salt in a medium bowl until well combined.
3. In a large heatproof bowl and using a hand whisk, whisk together the eggs, sugar, lemon juice and vanilla extract.
4. Set the bowl over a saucepan of gently simmering water. Whisk until the mixture reaches 110°F on an instant-read thermometer.
5. Using an electric mixer, beat the egg mixture on high speed until it becomes pale and thick, and falls in ribbons when the beaters are lifted, about 8 minutes.
6. Using a spatula, gently fold the flour mixture into the egg mixture, one-third at a time, folding just until combined after each addition.
7. Slowly pour the butter down the sides of the bowl. Fold it into the batter.
8. Immediately divide the batter evenly between the prepared pans. Bake until the cakes spring back when gently pressed and a wooden skewer inserted in the centre of the cakes comes out clean, 25 to 30 minutes.
9. Let the cakes cool in the pans on a wire rack for 5 to 10 minutes. Run a knife around the edges of the pans to loosen the cakes. Turn the cakes out onto the wire rack and let cool completely.
10. For the white chocolate cheesecake mousse, pour the lemon juice into a small bowl. Sprinkle the gelatin over the surface. Set aside until puffy, at least 5 minutes.
11. In a large bowl and using an electric mixer, beat ¾ cup of the cream until medium peaks form. Scrape the whipped cream into a medium bowl, cover and refrigerate until needed.
12. Put the white chocolate in a medium heatproof bowl. In a small saucepan, heat the remaining ¼ cup of cream over medium heat until it just comes to a simmer (do not boil). Pour half of the hot cream over the chocolate. Let stand for 30 seconds. Stir until combined. Add the remaining hot cream and stir until smooth.
13. Add the lemon juice–gelatin mixture to the chocolate. Stir until the gelatin is completely dissolved and the ingredients are well combined. Set aside.
14.  In a separate large bowl and using an electric mixer, beat the cream cheese until smooth. Scrape down the sides of the bowl. Beat in the vanilla extract.
15.  Add the white chocolate mixture to the cream cheese. Beat until well combined.
16. In a medium bowl and using an electric mixer with clean beaters, beat the egg white and salt until very frothy. Gradually add the sugar, beating until stiff peaks form and the mixture is glossy.
17. Using a spatula, fold the egg white into the cheese mixture until well combined. Fold in the whipped cream until well combined.
18. Stir the lemon extract into the simple syrup and let cool completely.
19. Grease an 8-inch round baking pan. Line the base with parchment paper. Cut a strip of parchment paper slightly longer than the pan’s circumference and 2 inches wider than its depth. Line the sides of the pan with the strip of paper so the paper extends 2 inches above the top of the pan.
20. Using a serrated knife, trim the tops of the cakes so they’re level. Place one cake, cut side up, in the prepared pan. Using a pastry brush, generously brush the cake with lemon simple syrup. Pour the mousse over the cake and smooth it level with an offset spatula. Refrigerate for 10 minutes.
21. Generously brush the top of the second cake with lemon simple syrup. Place the cake, syrup side down, over the chilled mousse, pressing down gently. Refrigerate for at least 4 hours, or overnight. (At this stage, the cake can be covered and refrigerated for up to 3 days.)
22. When ready to serve, whip the cream with the sugar in a medium bowl until soft peaks form. Carefully invert the cake onto a cake stand or serving plate. Peel off the paper. Pile the whipped cream on top of the cake. Garnish with lemon zest and lemon slices. Serve immediately.