Rinse the spinach well in a large bowl filled with water.

Transfer the spinach, drained but still wet, to a large braiser or sauté pan. Cover and let simmer over medium heat just until the spinach wilts.

Place the spinach in a colander and rinse quickly with cold water to stop it cooking. Drain and gently squeeze it dry. Then chop it finely.

Melt the butter in a large sauté pan or braiser and, if using, add the ham and let it sauté over gentle heat for a moment. Add the spinach and give it a good stir, seasoning generously with the salt. Sauté over lively heat for a couple of minutes, then turn off the heat. If using, grate over a tiny bit of nutmeg.

Meanwhile, bring a large pot of well salted water to a boil. Add the pasta and cook until al dente.

Drain the pasta, but not too well, and transfer it to pan with the spinach. Let it simmer for a minute, tossing or stirring from time to time.

Then add the ricotta, grated cheese and the other half of the butter. Mix well over the barest of flames. The pasta should flow easily. If not,add a ladleful of the pasta water and mix again. Taste and adjust for seasoning.

Serve immediately, with more grated cheese on the side for those who want it.