Wash the potatoes thoroughly and cook in plenty of boiling water for about 20 minutes. In the meantime, wash, quarter, seed and dice the tomatoes. Heat olive oil in a deep frying pan and simmer (melt) the tomatoes in it for 5 minutes.
Season with salt and pepper and set aside. Rinse potatoes under cold water, drain and peel. Press warm potatoes through a potato press. Add flour and egg, knead briefly and season with salt, pepper and nutmeg.
Shape the dough into rolls of approx. 1.5 cm Ø, cut into small pieces and form into balls with floured hands. Press flat with a fork. Boil up plenty of salted water in a large pot and let the gnocchi simmer in 2-3 portions.
When the gnocchi float on the surface, lift them out with a skimmer and drain well. Warm the finished gnocchi in the tomato sauce. Wash the basil, dab dry and cut into strips, except for a little to garnish.
Coarsely grate the ricotta and fold it into the gnocchi, except for a little bit for sprinkling. Sprinkle with the remaining ricotta and plenty of basil. Serve immediately garnished with the rest of the basil.