In a large bowl, combine the ricotta cheese, egg, grated Parmigiano-Reggiano, salt, and nutmeg (if using). Mix until smooth.
Gradually add the flour, mixing until a soft dough forms. The dough should be slightly sticky but manageable.
Dust a clean work surface with flour. Divide the dough into 4 portions.
Roll each portion into a long rope about 1 cm thick.
Cut the rope into small pieces (about 2 cm long) to form the gnocchi.
If desired, you can roll each piece on the back of a fork to create ridges, which helps the sauce adhere better.
Bring a large pot of salted water to a boil.
Gently add the gnocchi to the boiling water. Cook until they float to the surface, about 2-3 minutes.
Use a slotted spoon to remove the gnocchi and transfer them to a plate.
In a pan, heat olive oil or butter over medium heat.
Add the cooked gnocchi and sauté for a couple of minutes until lightly golden.
Serve garnished with fresh basil or parsley, and additional grated Parmigiano-Reggiano if desired.