Prepare the spinach: Bring a large pot of salted water to the boil. Add the spinach and cook for 30–40 seconds until wilted. Drain and refresh under cold water. Using your hands first, then a clean tea towel, squeeze out as much liquid as possible. Finely chop.

Make the gnudi mixture: In a large bowl, combine the ricotta, chopped spinach, egg, parmesan, flour, salt, pepper, and nutmeg. Mix gently until just combined — the mixture should be soft but not too wet. If it’s sticky, add a little more flour.

Shape the gnudi: Lightly flour your hands and roll the mixture into walnut-sized balls. Place them on a floured tray. Refrigerate for 20–30 minutes to firm up.

Cook the gnudi: Bring a large pot of salted water to the boil. If your pot is large enough, you can cook all the gnudi at once. Otherwise, work in batches. When the gnudi float to the surface, cook for 1–2 minutes more, then remove with a slotted spoon and transfer to a plate.

Make the sage butter: In a large frying pan, melt the butter over medium heat until it begins to foam. Add the sage leaves and cook until the butter turns golden brown and smells nutty. Remove the sage leaves and set aside to keep crisp.

Finish the gnudi in the pan: Add the cooked gnudi to the pan with the browned butter. Increase the heat slightly and cook for 1–2 minutes, gently turning so they brown lightly on all sides. Turn off the heat, then stir in the lemon zest.

Serve: Transfer the gnudi to plates, spoon over the butter, and sprinkle the crisp sage leaves on top. Finish with extra parmesan and serve immediately.