Make the pasta and roll into sheets to around No7 on the rolling machine (about 2 away from the thinnest setting). Keep them covered to avoid drying out, while you make the stuffing and sauce.
Making the Mezzelune
Heat a pan of lightly salted water until boiling.
Remove the cavolo nero from its stems and discard them. Chop the leaves roughly the tip into the boiling water. Cover and cook for 5 minutes, then drain and cool.
Once cooled slightly, tip the cooked cavolo nero into a clean tea towel. Gather up the towel and squeeze out as much liquid as you can.
Discard the liquid, then finely chop the cavolo nero. Set aside until cold.
In a bowl, mix together the ricotta, cavolo nero, Parmigiano Reggiano, nutmeg, salt and pepper. Mix until well combined, then set aside.
Take one of your pasta sheets and, using a pastry cutter (or something round, like a cup or glass) about 4"/10cm diameter, and cut the pasta into discs. Discard the excess pasta.
Take the stuffing and using your hands, roll a small ball, a little smaller than a ping pong ball. Place a ball in the centre of each disc.
Take a little water on your finger and lightly dampen half of a disc. Now bring together the two halves to form a semi-circle. Gently press around the edges to seal, trying to avoid any filling seeping out. Press into the mezzelune edges to seal as close to the stuffing as you can - this will avoid air pockets and potential bursting when cooking.NOTE - if you have too much filling and it seeps out, adjust the amount for your next.
Arrange the mezzelune on a waiting sheet of parchment paper or a tea towel (this will help you later).
Complete this process until you've run out of stuffing or pasta.
Dust the mezzelune in plenty of flour and cover with a tea towel - you can keep them for up to 4 hours before cooking.
Making the sauce
Heat a large frying over a moderate pan until just hot. Add the olive oil and heat for 10 seconds before add the garlic and sage. Let this sizzle gently for about a minute to season the oil. Now pour in the tomato and 1 cup water. Let it come to a gentle simmer.
Simmer gently for 5-8 minutes to reduce to a consistency of whipping/double cream. Remove from heat and season with salt & pepper.
Cooking the pasta
Bring a large pan of salted water to gently simme (don't have it boiling furiously, the pasta is delicate and could break apart).
Lift your paper or tea towel holding the pasta and gently slide all the pasta into the water at once. Give it a gentle stir and cook for 3-4 minutes until the pasta is cooked.
Return your sauce to a moderate heat. Using a slotted spoon gently remove all the mezzelune a from the water and into the sauce. Very gently toss the mezzelune into the sauce. Add a spoonful of the pasta water to loosen the sauce slightly and shake the pan to mix.
Spoon a few mezzelune and sauce into shallow bowls or plates and season with black pepper and more Parmigiano Reggiano (parmesan).
Video
Notes
Substitutions
Instead of cabbage you can use any green, leafy vegetable like spinach, kale, chard or nettles. Be sure to squeeze out the excess moisture in the same way.
Add herbs - for a subtle herbaceous flavour add a little fresh herbs to the stuffing mix. Try mint, oregano, basil or even tarragon.
Serving
Serve hot, sprinkled with a little parmigiana reggiano. I like a simple little salad afterwards of rocket, watercress or baby spinach with a lemon and olive oil dressing.
Storing
When fresh they'll only stay good for 3-4 hours - cover with a lightly dampened tea towel until you need them. There won't be any leftovers, so refrigerating is a moot point!
Freezing - Once stuffed, you can freeze them for 2-3 months. For the best results, add them to the freezer on a non-stick sheet pan in a single layer, not touching until solid. Then tip them into a bag and freeze. Freezing them separately first will help stop them sticking in the bag.