In a large mixing bowl, mix together the ricotta, eggs and grated cheese, together with a good pinch of salt and a scrape of nutmeg, until you have a uniform paste. Add the flour bit by bit until you get a soft but not sticky dough. Knead very briefly on a well floured surface to form a ball. Cover in plastic wrap, then a towel, and let rest for at least 30 minutes.
Cut the ball in halves or quarters, then roll out into thick logs, then cut the logs into lengths. (Each ndundero should weigh about 20-35g.)
Now press each length with your finger against the prongs of a fork, the side of cheese grater or, if you have one, a gnocchi board to form ridges on one side of each ndundero and a deep dimple on the other.
Repeat until you've used up all the dough. Lay out the ndunderi on a well floured tray or board until you want to cook them.
Simmer the ndunderi in well salted water 5 minutes or so. When they rise to the surface of the water let them go for a minute or two more, until done to your liking.
Using a skimmer, transfer them to a serving plate. Nap with your sauce of choice and serve right away, with additional grated cheese for those who like it.