Combine ricotta, parmesan, salt, and nutmeg in a large bowl. Add egg and stir until just incorporated. Starting with ⅓ cup at a time, gradually add flour, mixing gently until a dough forms. The dough should be soft but not sticky.
Lightly flour a clean work surface and turn out the dough. Knead gently until smooth, about 1 to 2 minutes. Avoid overworking it. Wrap the dough in cling wrap and refrigerate for at least 30 minutes.
When ready to shape, divide the dough into four pieces. Roll each piece into a long rope about 1 inch thick. Using a sharp knife or bench scraper, cut the ropes into 1-inch pieces. Lightly dust with flour and place on a parchment-lined baking sheet. If not cooking immediately, freeze the gnocchi in a single layer on the baking sheet, then transfer to a sealed container for storage.
Bring a large pot of salted water to a gentle boil. Add gnocchi and cook for about 3 minutes, or until they float to the surface.