For the jam croissants, first prepare a dampfl for the yeast dough as follows: Dissolve the yeast in the lukewarm milk and mix with about 200 g of the flour, cover and let rest in a warm place for about 30 minutes.
Stir the remaining flour, melted butter, cream, salt, rum, sugar and egg into the dampfl and knead into a smooth yeast dough. Cover the dough and let it rise in a warm place (about 1/2 hour).
Then divide the dough in half and roll out each piece. Cut out segments of about the same size from the round pieces of yeast and spread them with the jam, roll them up and shape them into croissants.
To rise, place the jam croissants on a baking tray lined with baking paper and allow to rise until they have visibly increased in volume. In the meantime, preheat the oven to 180°.
Before putting them into the oven, brush the surface of the croissants with a little beaten egg. Bake the jam croissants for about 20 – 25 minutes, until they have taken on a golden yellow color. Sprinkle with powdered sugar before serving.