First, make the filling by warming a heavy frying pan, dry over a medium heat.
Put the pine nuts in the pan and cook, shaking constantly until they brown. It should only take a minute or two, then transfer to a plate to cool.
Next, add the butter to the pan and, when melted, add the spinach and garlic and heat, stirring regularly until fully wilted.
Put the pine nuts and spinach mix into a food processor and blend until smooth.
Add the ricotta and whiz until smooth.
Finally, add the parmesan, pulse and then season to taste with salt and pepper.
Transfer to a bowl, cover and put in the fridge to chill while you make the pasta.
Prepare the pasta dough
Rinse and dry the food processor bowl, then start the pasta by adding the flour and pulsing 1 egg at a time until fully combined into a slightly sticky crumb.
Turn out onto a clean surface and kneed briefly into a smooth dough, then cut into quarters and wrap three sections.
Fill the ravioli
Make up a long strip of pasta either rolling by hand or with a pasta maker to almost the thinnest setting (I went to 7/8 out of 9).
Dust a surface with polenta and lay the strip out on it.
Spoon about the filling in equally quantities (about 1 level tablespoon) along the length of the strip, leaving a decent gap of 2-3 inches between each spoonful.
Take a new piece of pasta dough and create a second strip.
Brush a little water onto the bottom layer of pasta around each blob of filling, then place the second sheet of pasta carefully on top
Press firmly around each round of filling, pushing out the air and sealing well all the way around.
Cut out each of the ravioli rounds using the cookie cutter.
If piling them up, sprinkle polenta on top of each one or they'll stick together.
Repeat steps 1-7 for the remaining dough and filling - you should end up with 18-20 ravioli in total.
Place in a large pan of boiling water - they need just 4-5 minutes.
Prepare the sauce
While the pasta is boiling, melt the salted butter with the sage and heat for just a minute of so until the butter is melted and the leaves wilted.
Take off the heat and squeeze in the juice of half the lemon.
Drain and serve the pasta, then spoon up to a tablespoon of the clear butter and 3 or 4 sage leaves on top.
Finish with a few shavings of the hard cheese and serve.
If you'd like to make this pasta ahead and freeze, here's what to do. Place the ravioli in a single layer on a baking sheet dusted with polenta and freeze for an hour (this is so that they don't stick together). Once firm, you can transfer to a sealed bag or container. They should keep for up to 3 months.