Wash the plums and cut them halfway to remove the pits. Set aside.
Place the potatoes in a large pot with water and boil for 20 minutes, until tender.
Immediately peel the hot potatoes and place in a bowl.
Mash with the potato masher or a fork.
Add 30 g (2 tbsp) margarine and make sure the potatoes are mashed very finely.
Add semolina, flour, sugar and lemon peel. Mix with your hands until you have a soft and slightly sticky dough.
Bring 2 litres of water to a boil in a large pot.
Divide the dough into 7 equally sized pieces.
Place a little bit of oil in your hands to help shaping the dumplings and keep the dough from sticking.
Place a piece of sugar in each plum.
Shape one piece of dough into a disk and fold the dough around the plums.
Place in boiling water, reduce temperature and simmer for about 10 minutes.
Add remaining margarine to a pan and melt. Add bread crumbs and toast for a few minutes.
Roll the dumplings in the breadcrumb mixture and serve topped with powdered sugar.