For the rhubarb and topping cake, finely grind the walnut kernels in a blitz chopper for the dough. Mix 50 g ground nuts, flour, starch, baking powder, salt, egg yolk, sugar and butter in a mixing bowl with the dough hook of the hand mixer for about 1 minute until crumbles form. Line the bottom of the pan with baking paper, grease the edges. Press two-thirds of the crumble onto the bottom, forming a small rim. Chill the remaining crumble.
Clean the rhubarb, wash, drain and peel as desired. Cut into pieces about 3 cm long. Separate the eggs. Mix starch with 5 tablespoons of milk until smooth. Boil remaining milk with sugar and vanilla pulp. Add the stirred cornstarch and bring to the boil once, stirring vigorously with a whisk, until a very thick pudding is formed. Add the curd and egg yolks and bring to the boil once, stirring constantly. Remove the saucepan from the heat.
Preheat the oven to 180 °C. Beat the egg whites and powdered sugar until stiff, gently fold the beaten egg whites into the pudding.
Sprinkle the remaining walnuts on the pastry base. Spread the cheese cream on top, spread the rhubarb pieces on top. Sprinkle with the remaining crumble.
Bake the rhubarb and cheesecake in the oven (center, convection oven 160 °C) for about 45 minutes, then let the cake stand in the turned-off oven for another 10 minutes. Then take it out, let it rest for about 20 minutes, remove it from the pan and let it cool completely.