Blanch the spinach in boiling water or steam for 1–2 minutes, until softened. Cool enough to handle, then squeeze out as much water as possible. Finely puree the spinach. For frozen spinach, use 60–80 g (2.1–2.8 oz) after cooking and squeezing.
Blend the prepared spinach with the 3 eggs until evenly combined. Put the 00 flour on a clean work surface or in a bowl and make a well. Pour in the spinach–egg mixture, then add a little olive oil and a pinch of salt.
Gradually work the flour into the wet ingredients, then knead until the dough is smooth and elastic. Cover tightly and let it rest for 30 minutes. Keep the dough covered whenever you are not working with it. For guided lessons, explore my Pasta Mastery. Quick Start course. While the dough rests, mix the drained ricotta, Parmesan, mozzarella, egg yolk, salt, pepper, optional nutmeg and chopped basil or parsley. Keep the filling chilled until needed.
Divide the rested dough into manageable pieces. Roll each piece into a thin sheet with a pasta machine or rolling pin, lightly dusting with flour as needed. Keep the unused dough covered.
Shape the large spiral ravioli as shown in the video below. Add the cheese filling, fold the pasta around it and pinch the seams closed, gently pressing out trapped air. Coil into spirals without stretching the dough; seal the ends securely.
Bring a wide pan of salted water to a gentle boil. Cook the fresh ravioli in batches, allowing room for them to rise. Start checking after 1–2 minutes; they should float and the pasta should be tender, including at the seams. Thicker or frozen ravioli need longer. Lift out gently and reserve some cooking water.
Warm the butter and a little olive oil in a wide pan. Tear in the sage leaves and let them infuse gently. Add a splash of reserved pasta water and swirl until the sauce comes together. Add the cooked ravioli, coat gently and serve immediately.
