Swiss roll and vanilla mousse cake

Ingredients

For the Swiss roll sponge

• 5 eggs
• 1/4 teaspoon salt
• 3 tablespoons cold water
• 6 tablespoons sugar
• 6 tablespoons flour
• 1 teaspoon baking powder
• 1 tablespoon cocoa
• 1 teaspoon vanilla essence

For the strawberry jelly

• 200 g strawberries
• 3 tablespoons sugar
• 100 ml water
• 2 tablespoons cornstarch

For the cocoa sponge

• 5 eggs
• 1/4 teaspoon salt
• 150 g sugar
• 3 tablespoons water
• 3 tablespoons oil
• 125 g flour
• 1 teaspoon baking powder
• 25 g cocoa

For the syrup

• 100 ml water
• 100 ml strawberry syrup

For the vanilla mousse

• 4 egg yolks
• 250 ml milk
• 120 g sugar
• 1 vanilla bean
• 150 g sour cream 20% fat
• 300 ml whipping cream 30% fat
• 10 g gelatin
• 50 ml cold water

For the glaze and decoration

• 120 g milk chocolate
• 5 tablespoons whipping cream
• 100 g strawberries

Preparation

1. Preheat the oven to 180°C and line a 40 × 30 cm baking tray with parchment paper. Separate the eggs for the Swiss roll sponge. Beat the egg whites with 1/4 teaspoon salt and the 3 tablespoons cold water, then gradually add the 6 tablespoons sugar and beat until you have stiff peaks. 2. Fold in the egg yolks and vanilla essence. Sift the flour with the baking powder and gently fold it in, lifting the mixture from the bottom. Set aside 3 tablespoons of the batter, mix them with the cocoa and pipe a thin pattern onto the parchment paper. Bake for 3 minutes, until the pattern sets slightly. 3. Pour the plain batter into the tray and level it out. Bake for another 15 minutes, until the edges of the sponge are very lightly browned. Turn it out onto parchment paper, roll it up tightly while it’s hot and leave it to cool for 30 minutes in the paper. 4. Put the strawberries and sugar for the jelly in a saucepan and cook for 5 minutes, until the sugar melts. Purée the fruit. Dissolve the cornstarch in the 100 ml water, pour it over the strawberries and simmer for another 2 minutes, stirring, until the jelly thickens. Leave it to come to room temperature, about 30 minutes. 5. Carefully unroll the sponge, spread the jelly over it and set aside 2 tablespoons for assembling. Roll it up again and chill for 30 minutes. 6. For the cocoa sponge, beat the egg whites with 1/4 teaspoon salt and the sugar until you have stiff peaks. Add the water, egg yolks and oil, mixing on low speed. Mix the flour with the baking powder and cocoa, then fold them into the meringue. Pour the batter into the lined tray and bake for 20 minutes, until a toothpick comes out clean. Leave the sponge to cool for 30 minutes. 7. Cut the cocoa sponge into two uneven pieces: a smaller one for the base of the loaf pan and a larger one for the top. Boil the water for the syrup for 2 minutes, take it off the heat and stir in the strawberry syrup. Leave the syrup to cool for about 20 minutes. 8. For the mousse, put the milk and vanilla bean seeds in a saucepan and bring to a boil over about 5 minutes. Beat the egg yolks with the sugar until creamy. Slowly pour the hot milk over the yolks in a thin stream, whisking vigorously, then cook the custard over a double boiler for 10 minutes, until it thickens slightly. Leave it to cool for 30 minutes. 9. Soak the gelatin in the 50 ml cold water for 5 minutes, then melt it over low heat for about 1 minute, without letting it boil. Stir it into the egg yolk custard. Beat the sour cream and whipping cream until thick, then add the cooled custard and gently mix. 10. Line the loaf pan with plastic wrap and place the smaller cocoa sponge inside. Soak it with syrup, spread over the 2 tablespoons of reserved jelly and top with 3-4 tablespoons of mousse. 11. Trim the ends of the roll so it fits in the pan and place it on top of the mousse. Cover with the remaining mousse and the larger cocoa sponge, then soak it with syrup. Cover the pan and chill the cake overnight, at least 8 hours. 12. Turn the cake out onto a serving plate and remove the plastic wrap. Melt the chocolate with the 5 tablespoons whipping cream for 2 minutes, until the glaze is glossy, then spread it over the cake. Decorate with strawberries and thin strands of melted chocolate.