It’s strawberry season! I felt the urge to create a new dessert that would feature this spring fruit, and I thought, “Who doesn’t love chocolate and strawberries together?” The result: Strawberry-Mousse-Filled Chocolate Sponge Cake.

I began by converting my go-to sponge cake into a chocolate version, because I didn’t want a cake that was too heavy. It’s slightly heavier than the plain version. Then I converted my fruit-mousse recipe to a strawberry version, which I had never made before.

To view my other fruit-mousse recipes, click the following recipes: Pear Charlotte,  Passion Fruit Mousse.

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For the Chocolate Sponge Cake

Line the bottom of a 10-inch or 9-inch springform with parchment paper, and butter the paper, but not the sides of the pan. I used a 10-inch pan creating my Strawberry-Mousse-Filled Chocolate Sponge Cake. Preheat the oven to 350°. Be certain the eggs are at room temperature.

In a bowl whisk together the flour, sifted cocoa, salt, and baking powder.

Separate the eggs. In a large bowl beat the egg yolks and vanilla until thickened. Gradually beat in 3⁄4 cup of the sugar, and continue to beat until the mixture is very thick and forms a slowly dissolving ribbon.

In a slow, steady stream, beat in the vegetable oil, being certain that the mixture remains thick and homogenized.

In another bowl, beat the egg whites until foamy, and sprinkle on the cream of tartar. Continue to beat until soft peaks are beginning to form. Gradually beat in the remaining 1⁄4 cup of sugar until stiff peaks are formed.

Stir in 1⁄3 of the beaten egg whites into the yolk mixture with a rubber spatula to lighten the mixture.

Sprinkle 1⁄3 of the flour-cocoa mixture through a sieve into the batter and fold in carefully, using a J-shaped stroke.

Gently fold in the remaining 2⁄3 of the egg white and flour-cocoa mixture, alternately by thirds, ending with the egg whites.

It’s very important that you incorporate the whites and dry ingredients thoroughly, but this MUST be done carefully, gently, and without deflating the egg whites, which are the principal rising agent for the cake.

Pour the batter into the prepared springform and bake in the center rack of the oven. If using a 10-inch pan, the baking time should be about 25-30 minutes. If using a 9-inch pan, I would add another 5-7 minutes to the baking time. Remove the cake to a wire rack the minute a cake tester comes out clean, and let it cool for 10 minutes. Carefully remove the sides of the springform. Invert the cake onto the rack and carefully peel off the parchment paper. Allow the cake to cool thoroughly.

For the Sugar Syrup

Combine the sugar and water in a small saucepan and bring to a boil, stirring until the sugar is dissolved and the liquid becomes clear.

Let the syrup cool completely, then stir in the Kirsch. This syrup helps keep the cake moist, even after long refrigeration.

For the Strawberry-Mousse Filling

Wash and hull 1 quart of ripe strawberries. Place the sugar in a food processor and process for a few minutes until the sugar becomes very fine. (It’s nearly impossible to find superfine sugar any longer, so this process solves that issue.)

Add the berries to the sugar.

Continue to process, while pouring in the Kirsch or brandy, which intensifies the flavor.

Strain the puréed fruit through a fine sieve into a bowl.

Chill a bowl and beater you will use to beat the cream.

Place 1⁄3 of the puréed strawberries in a small saucepan, and sprinkle the gelatin over the mixture.

Over very low heat, warm the mixture, stirring constantly until the gelatin is completely dissolved.

Pour the gelatin-purée back into the bowl with the remaining strawberry purée. Place the bowl in ice water, stirring occasionally with a spatula until the mixture just begins to thicken. Do not let it set.

In the meantime, whip the heavy cream until medium peaks are formed. Do not over beat, or it becomes difficult to fold in.

Remove the gelatin-purée from the ice water, and stir 1⁄3 of the whipped cream into it.

Gently fold in the remaining whipped cream.

You want the mixture to be thick enough to spread without being too runny, but you do not want it to set. This may require refrigerating it until it reaches the right consistency. Check on it every few minutes to be sure it does not set.

For the Assembly

Split the cake in half.

Brush the cut side of each half with the sugar syrup. Use all of the syrup.

Wash, hull, and slice the remaining strawberries, setting a few aside for decoration. Dry the sliced strawberries on paper towels, so they won’t leak onto the mousse.

Place the top half of the cake, cut side up, back into the bottom of the springform. Pour half the mousse over the layer, and evenly arrange the sliced strawberries on the mousse.

Place the remaining layer, bottom side up, on top the mousse. This will give you a flat top. Pour the remaining mousse over top of the cake layer and smooth it out.

Refrigerate the dessert for several hours or overnight, until the mousse is fully set.

To serve the Strawberry-Mousse-Filled Chocolate Sponge Cake, remove the sides of the springform. Decorate the top of the cake with the remaining strawberries.

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