Clean, wash and cut the rhubarb into pieces. Put them in a pot and sprinkle with 125 g sugar; let them stand for about 15 minutes.
Add 200 ml water and 1 vanilla sugar, bring everything to the boil. Cover and simmer for about 5 minutes. Stir starch and 5 tablespoons of water until smooth. Stir into the boiling compote and simmer while stirring for at least 1 minute, sweeten if necessary.
Let it cool down.
Break meringue into small pieces. Whip the cream until stiff and allow 1 vanilla sugar to trickle in. Mix mascarpone, quark and 125 g sugar. Fold cream first, then 80 g meringue into the cream. Put the cream in a large bowl.
Spread the compote over it. Sprinkle the remaining meringue over it and sprinkle with cocoa.