Clean the rhubarb and cut into 2 cm thick pieces. Bring to the boil in a saucepan with 150 ml of water and sugar and simmer over a mild heat for 1 minute. Mix the custard powder with 1 tablespoon of water and stir into the rhubarb. Bring to the boil while stirring, transfer to a bowl and allow to cool completely. Clean and carefully fold in the strawberries.
Cut the ladyfingers into 2 cm pieces. Mix the mascarpone, powdered sugar and finished vanilla pudding until smooth.
Layer the ladyfingers, compote and vanilla cream in dessert glasses.