Beat the egg whites until stiff and add approx. 100 g sugar. Continue beating for about 2 minutes. Mix 120 g sugar, vanilla sugar and starch. Add 1 tsp. lemon juice to the beaten egg white and continue beating until the mixture is very firm and shiny.
Line a baking tray with baking paper. Preheat the oven (electric cooker: 150 °C/circulating air: 125 °C/gas: see manufacturer). Spread the beaten egg white mixture on the baking tray. Bake in a hot oven for approx. 25 minutes until the surface is crispy and the base separates easily from the baking paper.
Remove and leave to cool on the tray for about 5 minutes.
Place a sheet of baking paper on a rectangular cake rack. Dust thickly with icing sugar and carefully turn the meringue plate over. Remove the baked paper, which is now on top. Cover the meringue plate with a clean, slightly damp tea towel and let it cool down.
In the meantime, select the currants, wash them, drain them and remove them from the panicles with a fork. Stir mascarpone, 100 g sugar and 2 tbsp lemon juice until smooth. Whip cream until stiff and fold in.
Fold the berries, except for a few for decoration, under the mascarpone cream. Spread the cream on the meringue platter, leaving about 1 cm of edge free all around. Roll up from the long side using the baking paper.
Chill for about 1 hour. Decorate with the rest of the berries. Serve immediately.