Grease a square springform pan (24 x 24 cm; alternatively round, 26 cm Ø). Melt 75 g butter in a small pot, remove from heat and let it cool down a little. Crumble the oatmeal (see
Tip). Mix well in a bowl with the liquid butter. Put the crumbs into the springform pan and press them down with your hands to a smooth base. Chill for about 30 minutes.
Meanwhile, remove the seeds from the pumpkin, wash and dice with the skin. Weigh 380 g and boil up with 200 ml water. Cover and cook for about 8 minutes, then drain well and let cool. Then put the pumpkin into a high mixing bowl and puree it finely with a hand blender.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Cream eggs, sugar, vanilla sugar and 1 pinch of salt with the whisks of the mixer. Let the oil run in while stirring.
Add yoghurt and baking powder, stir well. Stir in pumpkin. Pour the mixture onto the crumb base.
Bake in a hot oven for 1-1 1⁄4 hours. If necessary, cover the cake with aluminium foil after about 40 minutes baking time. Remove from the oven, place on a cake rack and let it cool in the tin. Remove the cake from the mould and dust with icing sugar.
Cut off 4 pieces and arrange. Eat the rest in the next 3-4 days or wrap it up nicely for the guests. Chocolate sauce tastes good with it.