For the strawberry slices, bake thin sponge cake according to instructions.
For the foam, whisk egg whites with 50 g sugar and vanilla sugar until foamy. Mix 80 g sugar with agar agar, add to boiling water, boil briefly and stir until powder dissolves.
Add 310 g sugar, boil and stir until dissolved. Beat egg whites until stiff. Fold the sugar mixture into the snow while it is still hot. Stir gently until the mixture is only lukewarm, but already stable again. Place sponge cake base in a baking frame (26×36) and spread with apricot jam. Place strawberries on top, spread with 3/4 of the foam mixture. Spread the remaining mousse on top of the mousse in a grid pattern.
Bake the strawberry slices at 250°C until lightly browned.
Decorate the strawberry slices with whipped cream before serving.