Raspberry filling:

Cup of Yum
1. Cook: Place the frozen raspberries and the sugar in a small saucepan. Mix and leave to defrost while you make the sponge. Once defrosted or almost so, turn on the heat. Bring to a boil and boil gently for 5 minutes, stirring often. Remove and leave to cool until needed.

Sponge:

1. Preheat the oven to 200 degrees Celsius/ 400 degrees Fahrenheit. Line a baking tray with baking paper.
2. Eggs: Separate the eggs. Beat the egg whites with a pinch of salt until quite stiff. Gradually add 2 tablespoons of the granulated sugar and beat until glossy and stiff. Set aside.In another bowl, whisk together the egg yolks and 2 tablespoons of sugar until foamy.
3. Mix flour and cornstarch. Sieve over the egg yolk-sugar mixture. Sprinkle 1 teaspoon of the lemon zest on top. Add ⅓ of the egg whites and incorporate. Add the remaining egg whites and fold in gently.
4. Bake: Spread the batter onto the baking tray. Bake for 8 to 10 minutes until golden.
5. Roll: In the meantime, place a clean kitchen towel on the table and sprinkle it with icing sugar. Turn the cake onto the kitchen towel with the baking paper facing up. Carefully peel off the baking paper, then immediately roll the cake with the help of the towel. Leave it until completely cool; it should take about 1 hour.

Mascarpone filling:

1. Beat mascarpone, sugar, lemon juice, and vanilla extract until creamy. Slowly start pouring in the heavy cream while mixing continuously. After one minute, sprinkle the cornstarch and lemon zest over the mixture. Continue beating until the cream is nicely whipped and fluffy.

Assemble:

1. Fill: Unroll the sponge and spread the raspberry filling evenly onto it. Cover with the mascarpone cream.
2. Roll the roulade again carefully. Wrap in plastic foil/cling film, place on a platter.
3. Refrigerate for 2 to 4 hours or until nicely set. Remove the wrap.
4. Whip the heavy cream with sugar and vanilla extract. Pipe the cream onto the roulade. Decorate with fresh raspberries and thinly cut lemon slices.