For the plum-poppy seed macaroons, boil the dried plums with milk, add the poppy seeds, allow to steep for a while and cool.
Beat egg whites with sugar until very stiff. Take a pastry card full of it and stir well into the poppy seed mixture.
Mix remaining beaten egg whites, poppy seed mixture, hazelnuts and cinnamon with a wooden spoon. Fill into a piping bag with a smooth nozzle and pipe small bushels onto a prepared baking sheet. Bake in the preheated oven at 160 to 170 °C for 11 to 13 minutes until light.
Spread half of the cooled plum-poppy seed macaroons with jam on the underside and assemble with the other half. Dip in chocolate glaze if desired.