redcurrants or other berries, to decorate (optional)
Line a baking sheet with baking paper.
Place the frozen fruits in a bowl or food processor with the mascarpone, vanilla paste, icing sugar and crème de cassis or cranberry juice. Beat or pulse until very thick and smooth.
Spread the fruit mixture over the sponge base in a thick, even layer. Place on the prepared baking sheet, then cover loosely with clingfilm and chill in the freezer for about 15 minutes.
Meanwhile, make the meringue mixture by whisking the egg whites until they form soft peaks. Gradually add the caster sugar, a spoonful at a time, whisking well between each addition, until the meringue is thick, glossy and forms stiff peaks.
Spoon the meringue mixture over the flan, using the back of the spoon to create peaks. Slide under a preheated hot grill for 1–2 minutes, until the top is beginning to colour nicely.
Cut into wedges, decorate with redcurrants or other berries, if desired, and serve immediately.