First of all, you will need fresh plums!
Then you can do the rest.
The dough is made of mashed potatoes, eggs and flour. For around 14 plum dumplings you will need:
2 boiled potatoes,
and flour (add flour until you get soft, compact dough).
Now everything depends on your taste. If you like more dough, you will use more dough for one plum. You can put a half plum, or whole if you like it more fruity. I like plums more than dough, so I use whole plum and dough just to cover it (average thickness is about 0,5 cm). When you wrapped all the plums, place them in a pot with boiled water. Leave it until plum dumplings get to the top of the pot. They need around 15 minutes to get cooked.
Put sugar and crumbled corn flakes in a frying pan and heat it. Place the cooked plum dumplings into it and carefully stir it up until cornflakes stick to them.