Yield: 6 Servings

Trifle cake:
• 1¼ cups all-purpose flour
• 2½ teaspoons baking powder
• Pinch of salt
• 5 large eggs, separated
• 1¼ cups sugar
• 5 Tablespoons very hot water
• 1½ teaspoons vanilla extract

White chocolate mousse:
• 4 large egg yolks
• ¼ cup sugar
• 3 Tablespoons Grand Marnier
• 3 Tablespoons water
• 1½ teaspoons lemon juice, freshly squeezed
• 3 ounces white chocolate, finely chopped
• 1 cup heavy whipping cream

Berry sauce:
• 12 ounces frozen strawberries or raspberries (no sugar added), defrosted
• 2 Tablespoons sugar, or to taste
• 1 pint fresh strawberries
• 1 pint fresh raspberries
• 1 Tablespoon sugar, or to taste

Sift together flour, baking powder, and salt.

In a medium bowl with an electric mixer, whip together egg yolks and sugar on high speed until thick and smooth, about 2 minutes with a stand mixer or 4 minutes with a handheld mixer. Reduce to low speed and add hot water and vanilla. Scrape down sides of bowl. Increase speed to high and whip until thick, about 1 minute. Reduce speed to low and stir in dry ingredients.

In another bowl with an electric mixer, whip egg whites until soft peaks form, about 1 minute with a stand mixer or 2 to 3 minutes with a handheld mixer. Fold egg whites into batter. Spread batter evenly and gently into the prepared jelly roll pan.

Bake cake until it is golden brown in color and springs back lightly when touched on top, about 20 minutes. Let it cool to room temperature.

For white chocolate mousse:
Whisk together egg yolks and sugar in a medium stainless-steel mixing bowl. Stir in Grand Marnier, water, and lemon juice. Set bowl over a pot of simmering water, making sure the bottom of it does not touch the water. Whisk eggs briskly until the mixture has thickened and tripled in volume, about 2 to 3 minutes.

Remove bowl from stove and whisk in white chocolate until smooth. Let cool to room temperature, stirring occasionally. Whip the cream until soft peaks form, then fold it into the white chocolate mixture.

For berry sauce:
Purée frozen berries in food processor or pass through a food mill. Strain the purée through a fine-mesh sieve and discard seeds. Stir in sugar. Add another 1 to 2 Tablespoons of sugar if the sauce is not sweet enough.

To assemble the trifle, run a knife around the inside edge of the pan and invert it onto the counter. Carefully peel off parchment paper. Cut cake into quarters. Cut each piece in half horizontally.

Hull and quarter strawberries; cut them into sixths if they are big. In a medium bowl, gently stir them together with half of the raspberries and sugar. Taste the berries – if they are not sweet enough, add another Tablespoon of sugar.

Place a spoonful of berries in the bottom of 6 individual parfait or wine glasses. Spread a single layer of the white chocolate mousse over the berries. Cut cake pieces to fit a single layer over the cream. Spread some berry sauce over the cake, completely covering it. Continue layering more berries, mousse, cake, and sauce until you finish with a layer of mousse on top. There will be leftover cake, which can be frozen for another use. Arrange the remaining raspberries around the top of the trifles. Refrigerate trifles for several hours before serving.

Packing tips:
The cake can be made several days in advance, wrapped in plastic wrap, and stored at room temperature. The cake is easier to cut if it is a day old. The white chocolate mousse can be made a day ahead and kept refrigerated. The berry sauce can be made 2 days in advance and kept refrigerated. The trifles can be assembled a day before they will be served and kept refrigerated. To serve these trifles at your picnic, use clear, disposable plastic cups instead of parfait cups or wine glasses. Cover each trifle with plastic wrap and hold it in place with a rubber band.