Tip the spinach into a sieve and press out the excess water, then add to the bowl of your food processor along with the eggs and egg yolk. Blitz until you have a smooth green liquid.
Add the flour to the food processor. Start pulsing the motor. You'll need to scrape down the sides and bottom of the blender bowl a few times to ensure everything is combined into a clumpy, vibrant green dough. Gather the dough and transfer to a clean surface.
Knead until you have a smooth, even dough, then cover with cling film and leave to rest for 20-30 minutes to make it easier to work with.
Roll and cut the tagliatelle verdi
Divide the pasta dough in half, working one piece at a time whilst keeping the other wrapped to prevent it from drying out.
Shape the piece into a rectangle and set the pasta machine to its widest setting. Pass the pasta through the machine, then fold up and pass through again at 90 degrees from the folds. Repeat until you have a smooth sheet without tears, splits or dry patches.
You can now reduce the number on your machine by one and pass the pasta through again twice. Keep working down the numbers, passing the pasta through twice each time and dusting with a tiny bit of flavour if it sticks until you are down to the penultimate setting (e.g. if your machine runs from 7 down to 1, stop at setting 2).
Dust the underside of the strip very lightly with flour so that it doesn't stick and lay it out flat. Cut it in half so that you have two shorter strips, side by side.
Repeat with the other piece of dough.
Give all the sheets 5-10 minutes to dry out a bit - turning halfway to allow them to dry on both sides. Your pasta sheets should lose their stickiness but should not be left so long as to go stiff or brittle.
Starting with the first ones you made, start running your sheets through the pasta machine’s tagliatelle setting one by one.
As you roll your tagliatelle, there is a danger of it clumping together if left to sit. To avoid this, you have two options...
You can dust your tagliatelle lightly with semolina and form into little nests on a tray.
Alternatively, you can hang your tagliatelle verdi on a pasta drying rack or improvise something similar. When my kids were babies, I'd tie baker's twine between two kitchen cabinet handles and hang the pasta that way!
Cook the tagliatelle verdi
Fill a large pot with boiling water. Add plenty of salt - Italians say it should be as salty as the sea. When you have a fierce rolling boil, add the tagliatelle verde and boil for 3-5 minutes until al dente.