Mix 10 g sugar, flour, salt, egg, oil and beer to make a batter.
Rinse the plums, dry them with paper towels, cut them in half and remove the seeds. Turn them to the other side in the remaining 2 tbsp. flour and then pull them through the batter with 2 forks. Bake in portions in the 180 °C hot fat (in the deep fryer or possibly in a saucepan on level 10 of the automatic plate) for 3-4 minutes until golden brown.
For the sauce, place the eggs, sugar and cognac in a saucepan and beat at a moderate temperature (speed 3 on the automatic plate) with the whisks of a mixer until a foamy cream is formed. Serve warm with the doughnuts on the table.