Lemon Mousse Layer Cake

White Cake 1/4 stick butter, room temperature 1/2 cup plus 1 tablespoon cake flour1 1/2 teaspoons baking powder 1/2 teaspoon salt 2/3 cup sugar 1/3 cup milk, room temperature2 teaspoons vanilla3 egg whites, room temperatureLemon mousse 3/4 teaspoon unflavored gelatin1 1/2 ounces cold water5 tablespoons lemon juice3 ounces white chocolate1 cup minus 1 1/2 teaspoons heavy creamHeat oven to 350 degrees. Grease an 8-inch round cake pan.For the cake: Cut butter into cubes. Sift together flour, baking powder and salt in the bowl of a stand mixer. Add flour and mix on low speed for 2 minutes. Add half of milk and sugar, mix on low for 2 minutes. Scrape bowl.Combine remaining milk, vanilla and eggs. Add to mixing bowl in thirds, scraping bowl before each addition. When all has been added, mix on low 5 minutes. Pour batter into prepared pan and bake until center of cake springs back when lightly pressed. Cool on rack completely.For the lemon mousse: Sprinkle gelatin over cold water; do not stir.In a medium bowl, whip heavy cream to soft peaks and set aside.Place white chocolate into mixing bowl. In small saucepan bring lemon juice to a simmer. Add softened gelatin and stir until completely dissolved. Pour over white chocolate and whisk until all chocolate is melted and mixture is smooth. Pour chocolate mixture into whipped cream and fold together until combined.To assemble: Slice cake horizontally into two layers. Place one layer on serving plate, top with half the mousse. Repeat with second layer and remaining mousse.Serves 10 to 12.Joshua Johnson, pastry chef/co-owner, Cocoa Bean Fine Desserts, Geneva