Put the pasta flour into a food processor and add the egg and olive oil. Pulse until the mixture resembles breadcrumbs. Tip into a bowl and bring together with your hands to form a ball of dough. Transfer to a lightly floured board and knead until smooth (don't worry if the dough feels a bit stiff, as it will soften slightly on resting). Wrap in clingfilm and set aside to rest for 20 minutes.
In a bowl, mix the ricotta, herbs, Parmesan and some seasoning. Set aside.
Cut the dough in half, then roll out each piece in a pasta machine, dusting with flour to stop it sticking. Use the thickest setting for the first three passes, folding the sheet into three before putting it through again, then reduce the settings as you continue until you have a very thin, almost transparent sheet of pasta measuring roughly 85x9cm (33x3 1/2in). Cut the large pasta sheet in half to get two shorter lengths. Repeat with the remaining dough, until you have four sheets of pasta in total. If you don't have a pasta machine, divide the dough into four pieces and use a rolling pin to roll them out as thinly as possible into long rectangles.
Lay the pasta sheets on a board dusted with a little flour. Dollop 5tsp of the ricotta filling along 2 of the sheets, leaving a little gap between each. Brush a little water around the mixture, then loosely cover each piece with one of the remaining pasta strips. Working quickly, seal the sheets together by pressing around the blobs of filling, extracting any air. Cut into squares using a pasta cutter or sharp knife to make 10 ravioli. If you have time, leave them on a wire rack to dry for 30 minutes.
Bring a large pan of salted water to the boil. Using a slotted spoon, gently lower the ravioli into the pan and cook for 3-5 minutes or until they float up to the surface.
Meanwhile, melt the butter in a frying pan until foaming. Add the sage leaves and cook on both sides. Stir in the pine nuts, then season well and remove from the heat.
Using the slotted spoon, lift the ravioli out of the pan, draining well. To serve, divide them between two plates, then spoon over the buttery sauce, sage, and pine nuts. Add a squeeze of lemon and serve immediately with extra Parmesan scattered over.