Peel, wash and halve the potatoes and cook in boiling salted water for about 20 minutes.
Heat oil for the filling. Fry the ham until crispy, turning it over. Peel onions and cut into fine cubes. Add onions and tomato paste and mix. Squeeze out the sauerkraut, add to the bacon onions and sauté briefly. Season to taste with salt, pepper, caraway and sugar. Put the sauerkraut in a cool place.
Drain the potatoes well and press them through a potato ricer. Add flour, semolina and egg and mix to a loose dough. Season to taste with salt and pepper. Let the dough swell for about 10 minutes.
Divide the dough into 12 portions of equal size. Form the dough portions into circles (approx. 12 cm Ø) of uniform thickness on a well floured work surface. Spread the sauerkraut evenly over the circles. Fold half of the circles into semicircles. Gently press the edges together with your fingers. Place on 2 baking trays lined with baking paper. Whisk the egg yolks and milk and spread a thin layer on the dumplings. Bake one after the other in a preheated oven (electric range: 200 °C/ convection oven: 175 °C/ gas: level 3) for about 15 minutes.
Wash the chives, shake dry and cut into fine rolls. Mix cream and chives and season to taste with salt and pepper. Arrange the dip together with the dumplings.