Grease a springform pan (26 cm Ø) and dust with flour. Separate 1 egg. Knead the flour, 75 g sugar, 1 packet of vanilla sugar, 1 pinch of salt, butter in pieces, 1 egg yolk and 1-2 tbsp cold water first with a hand mixer and then briefly with your hands until smooth.
Roll out the short pastry to a circle (26 cm Ø) on a little flour. Place it on the bottom of the springform pan and prick it several times with a fork. Chill for about 30 minutes.
Bring the milk to the boil and stir in the poppy seeds, 100 g sugar, 1 packet of vanilla sugar and 1 pinch of salt. Bring to the boil again while stirring, simmer for 2-3 minutes and remove from the heat. Let it cool down for about 10 minutes, stirring more often.
Mix sour cream, 3 eggs, sauce powder and 75 g sugar. Wash, peel, halve and core the pears. Stir 1 egg white and 2 eggs into the poppy seed mixture.
Sprinkle the short pastry base with breadcrumbs. Spread the poppy seed mixture on top and smooth it down. Place the pears next to each other in a circle with the cut surface facing down and press them lightly into the mixture.
Carefully pour the sour cream mixture over the pears. Bake in the preheated oven (electric cooker: 200 °C/circulating air: 175 °C/gas: level 3) for approx. 70 minutes.
Remove the cake from the oven, place it on a cake rack, remove it from the edge of the springform pan with a knife and let it cool in the pan for about 4 hours. Remove from the mould and dust the top edge with icing sugar.