Clean, wash and cut the rhubarb into pieces. Mix in a pot with jam sugar and let it stand for about 30 minutes. Then heat up while stirring. Let it boil for about 3 minutes while stirring. Put a sample spot on a plate when the mixture is gelling, pour everything into a bowl. Let it cool down a bit, put it in a cold place and let it cool down, stirring every now and then
Line a baking tray (inside dimensions 24 x 36 cm) with baking paper and spread a thin layer of oil on it. Beat the egg white with the whisk of the hand mixer until stiff. Let about half of the sugar trickle in and continue beating for a few minutes. Mix the remaining sugar, 1 packet of vanillin sugar and starch. Add the vinegar and continue beating until the mixture is very firm and shiny
Pour onto the baking paper and spread evenly. Bake in the preheated oven (electric cooker: 150 °C/ convection oven: 125 °C/ gas: level 1) 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 a few minutes. Place 1 piece of baking paper on a rectangular cake rack and dust thickly with icing sugar. Turn the meringue plate over onto the baking parchment, remove the baked paper. Cover the plate with a slightly damp cloth and let it cool down
Mix yoghurt with 1 sachet of vanilla sugar until smooth. Pour onto the meringue platter and spread, leaving an approx. 1 cm wide rim all around. Spread the rhubarb compote on top in large blobs. Roll up from the short side. Decorate with lemon balm and dust with 1 tbsp. icing sugar, chill briefly and serve immediately.
waiting time 2 hours