Prepare rhubarb (ready to cook, e.g. peel, remove woody parts and dirt), cutting thick stalks in half lengthwise. Cut rhubarb into pieces about three inches long. Place rhubarb, sugar and vanilla sugar in a frying pan with very little water and cook until just tender, stirring frequently. Cool.
Coarsely chop ladyfingers or amaretti. Spread evenly on the bottom of well-buttered ovenproof ramekins. In each ramekin, mold two tablespoons rhubarb compote, preferably without liquid, and press a little smooth so that rhubarb and crumbs “combine”.
Mix eggs, milk, cream, vanilla sugar and sugar. Pour over the rhubarb in the ramekins. Place them in a larger ovenproof dish. Pour boiling hot water around them so that the ramekins are well halfway in the water bath. Meanwhile, bake the rhubarb patties in the oven heated to 150 degrees on the middle shelf for about fifty minutes. Serve lukewarm.