Put flour, 250 g butter in flakes, icing sugar, egg and vanillin sugar in a bowl. Knead first with the dough hooks of the hand mixer, then with your hands to a smooth shortcrust pastry. Wrap the dough in foil and chill for about 30 minutes.
Bring 2 tablespoons of butter, cream and sugar to the boil in a saucepan while stirring. Simmer at medium heat for about 10 minutes. Add pumpkin seeds and simmer for another 5 minutes. Take the pot off the stove and let it cool down for about 15 minutes.
Roll out the short pastry rectangularly (approx. 32 x 38 cm) on a floured work surface. Using the dough roller, place the dough in a greased, floured fat pan of the oven (32 x 38 cm).
Spread pumpkin seed mixture on it. Bake in the preheated oven (electric cooker: 200 °C/ circulating air: 175 °C/ gas: see manufacturer) for 10-12 minutes. Take out and let cool on a cake rack.
Cut lukewarm into isosceles triangles (each side approx. 5 cm).