Two layers of crisp, chewy meringue filled with a rich whipped mascarpone cream. Everything must be well chilled.

Whip the egg whites until stiff peaks form — test by turning the bowl upside down over your head, nothing should fall. Slowly add the powdered sugar, a little at a time, continuing to whip until glossy and firm.
Fold in the potato starch and vinegar. Divide the meringue equally and shape into 2 round layers on baking paper.
Bake both sheets at the same time at 170°C fan for 10 minutes, then lower to 140°C and bake for a further 80 minutes.
Leave to cool completely in the oven with the door ajar.
The cream must be cold. Whip the well-chilled heavy cream together with the vanilla sugar until firm.
Add the mascarpone and fold/whip briefly until combined — do not overwhip once the mascarpone is in.
Spread the cream over the first meringue layer, place the second layer on top, and finish with the remaining cream. Refrigerate until serving.
Photos from the process.

