For the rhubarb cannelloni, first boil wine with sugar. Add the rhubarb and cook for 3 minutes. Stir the pudding powder with a little water until smooth, thicken the rhubarb with it.
Fill cannelloni with it (if necessary, pre-cook according to package instructions). Layer in a greased baking dish, pour on the remaining compote. Spread with mascarpone. Bake the rhubarb cannelloni in the oven at 200 degrees for 25-30 minutes until the surface is golden brown.