You can make mashed potatoes in several ways. The best way would be baking the potatoes, then carving out the flesh.

Or even simpler, I boiled the potatoes without the skin. As soon as they were done, I drained and mashed them, hot as they were.

Let it cool. This can be done 1-2 days before and kept in the fridge.

Prepare the plums. Wash well, cut to the core with a knife and carefully remove the pits.

If the plums are small, leave them whole. If they are bigger, cut them into medium-sized pieces.

Sprinkle with three tablespoons of sugar over the plums and one teaspoon of cinnamon, set aside.

Now, melt the butter in a saucepan, add the breadcrumbs and mix periodically until nicely browned.

When it's browned, turn off the heat. Add sugar and, optionally, vanilla  essence, powder or seeds.

Now we start to make the dumpling dough.

I actually measured 500g of mashed potatoes. I used the leftovers as a garnish for another meal.

Put the egg and oil over the potatoes and a little salt.

Add the flour and mix well with your hands. You'll get a rather sticky and soft dough, but don't add any more flour, if you want your dumplings to be tender.

Turn the dough out onto the table dusted with flour and knead a little until smooth. Sprinkle with some flour so that it won't stick to the table.

Cut into medium pieces, about the size of a walnut. Here, it depends on the size of your plums, if they are whole or pieces.

You'll see how big the dough pieces should be when you start to shape the dumplings (you can even make a sample).

Sprinkle with some flour on your hands. Take a piece of dough and flatten it out between your palms.

If the plum is whole, place it cut side down and cover it completely with the dough by gluing the edges together.

Something like this. Even it out in your palm so that it looks like a smooth ball.

Out of these quantities, I made 18 medium-sized dumplings. I arranged them on the floured table.

Place over heat a pot half filled with water (you can do this while shaping the dumplings).

When it comes to the boil, add three tablespoons of sugar, if you want the dumplings to be sweeter.

When the water comes to the boil, turn down the heat and sink the dumplings in.

At first, they will go to the bottom, then rise to the surface. If they stick to the bottom of the pot, shake it lightly or peel them off carefully with a spatula.

Let simmer for 10-15 minutes, depending on how well cooked you want the plums to be. You can leave them for 5 minutes, but the plums will be a little raw.

I boiled the dumplings in two batches, nine at a time, in a five liter pot. 

After they have boiled, place them straight in the pan with the breadcrumbs and coat on all sides.

Serve the dumplings hot or cold. I liked them better when they were cold, but this depends on your tastes.

Enjoy!