Clean the rhubarb, remove the peel and cut into pieces about three centimeters long. Bring to a boil with the water, sugar and juice of one lemon, with the lid closed. The rhubarb pieces should remain whole and only become half-cooked.
Drain the rhubarb. Repeatedly add the juice to the skillet and boil until half cooked. Spread the jam through a sieve. Add together with kirsch and orange liqueur, respectively. Stir through with the cornstarch and bring to a boil until a syrup forms. Cool.
Whip the cream (1) until stiff. Butter a gratin dish or small egg pans.
Spread the rhubarb pieces evenly in the dish or the egg patties.
Whip the yolks with the cream (2) to a cream. Mix with the prepared syrup and the whipped cream. Spread this glaze evenly over the rhubarb. Bake in the oven at 180 °C for about fifteen minutes.
Sprinkle the gratin with the powdered sugar and gratinate for a few more minutes at high top heat.
Let the gratin stand for fifteen to twenty min. after it is done, so that it cools down a bit. Serve lukewarm in the dish.
Tips For this gratin, use only a shallow mold or egg squares so that the cream sets evenly and quickly. It should not become dry and should therefore not set too firmly. It is best to check after ten minutes of baking with the tip of a knife whether the glaze has set.