Pour the plums into a sieve and let them drain. Collect the juice. Stir 5 tbsp. juice and sauce powder until smooth. Boil up the rest of the juice and vanilla sugar. Stir in 1/2 packet of sauce powder and simmer for about 1 minute.
Remove the pot from the stove and let it cool down while stirring occasionally.
Mix 5 tablespoons of milk and the remaining sauce powder. Bring 200 ml milk and 2 tablespoons sugar to the boil. Stir in sauce powder and simmer for about 1 minute. Remove sauce from the stove and let it cool down while stirring occasionally.
Cream fat, salt and 40 g sugar with the whisk of the hand mixer. Stir in the eggs one by one. Mix flour and baking powder and stir in alternately with the buttermilk.
Add the plums to the plum juice and mix. Grease the waffle iron for 2 rectangular waffles (approx. 12 x 21 cm). Put a heaped tablespoon of batter into each rectangle and bake for 3-5 minutes until golden brown.
Process the remaining dough in the same way (15-18 wafers). Dust the waffles with icing sugar and serve with plum compote. Serve with vanilla sauce.