Separate 1 egg. Chill the egg white. For the short pastry, put flour, 75 g sugar, salt, 1 packet of vanillin sugar, egg yolk, 1-2 tbsp water and butter in flakes in a bowl and knead first with the dough hooks of the hand mixer, then with your hands to a smooth short pastry. Roll out to a circle (26 cm Ø) on a floured work surface. Pour it onto the bottom of a greased, flour-spread springform pan (26 cm Ø), press it down slightly, prick it several times with a fork and chill it for about 30 minutes.
In the meantime boil up the milk. Add the poppy seeds, 1 packet of vanilla sugar, salt and 100 g sugar, bring to the boil again while stirring. Simmer for 2-3 minutes at low heat, remove from the heat and let cool down for about 10 minutes while stirring
For the sour cream icing, mix sour cream, 3 eggs, sauce powder and 75 g sugar. Wash, peel and halve the pears, cut out the core. Stir egg white and 2 eggs into the poppy seed mixture. Sprinkle the short pastry base evenly with breadcrumbs. Add the poppy seed mixture and smooth it down. Place pears in a circle with the cut surface facing down, press lightly. Carefully spread the frosting over the pears.
Bake in the preheated oven (electric range: 200 °C/ convection oven: 175 °C/ gas: level 3) on the lower rack for 50-60 minutes. Remove from the oven, place on a grid, remove from the edge of the springform pan with a knife and allow to cool in the pan. Remove from the mould and dust the rim with icing sugar as desired. Arrange on a cake plate