Make sure to use freshly grated Parmigiano here and grate it on a rasp grater; the pre-grated kind will make the filling gritty. You can freeze the tortellini right on the baking sheet until solid, then pack them in resealable freezer bags and freeze for up to 3 months. Cook them directly from frozen adding an extra minute or two to the boiling time. Always keep the dough you’re not working with covered with a kitchen towel so it doesn’t dry out, which would make it harder to seal. If you’re cooking the full batch of tortellini at once, use your largest pot so the tortellini won’t crowd the pot and stick together.