Mix flour, semolina, eggs, olive oil, salt and half the water and knead them in your kitchen machine to form a smooth dough. Only add the remaining water if necessary. If you don't use a kitchen machine, pour the flour and semolina onto your work surface, make a whole in the center where you add the eggs, olive oil, salt and half the water. Then knead until you have a smooth dough, only adding the remaining water if necessary.
Wrap the dough in plastic and let it rest for 30 minutes.
While the dough is resting, mix the ricotta homemade or shop-bought, parmesan, lemon zest, salt, pepper, yolks and thyme leaves in a bowl. Add the cream if you are using it. Then form little balls using the filling. I made mine 4 cm in diameter for the bigger raviolo and 2 cm in diameter for the smaller ravioli. But you can decide for yourself which size you want to go for. It all depends on the size of your cookie cutter, which I use to cut out the dough disks. I used a round cookie cutter 9 cm in diameter for the top disk and and a cutter 7 cm in diameter for the bottom disk preparing the larger raviolo. For the smaller ravioli I used a 4 cm square cookie cutter for the bottom disk and a 5.5 cm cookie cutter for the top disk. Just as a guideline.
After the pasta dough has rested, roll it as thin as possible out on your flour and semolina-dusted work surface and cut two discs out per ravioli or raviolo. Put one ricotta ball in the middle of the smaller dough disk, damp the surrounding of the ricotta ball lightly with water and cover the ball with the second (larger) disk. Carefully fold the top disk around the ricotta ball and avoid to trap air underneath the dough disk. Press the rim firmly around the ball and put the ravioli on a semolina-dusted baking sheet. Proceed in the same way with the rest of the dough and ricotta balls. Cover the ready-made ravioli with a damp tea towel to prevent them from drying out.
Boil some salted water in a large pot and cook a few ravioli for approximately 3 minutes at a time. They float on the surface when they are ready. Don't let the water boil vigorously, only let it simmer, otherwise you could end up with a split ravioli. Keep the ravioli warm while you cook the other batches.
Serving suggestionI like to serve the ravioli or raviolo with some lemon-infused olive oil, some freshly grated parmesan cheese, freshly grated lemon zest, lots of freshly-grounded black pepper and a few thyme springs. If I have some pasta dough left over, I roll it out and cut it into thin strips and I finally have fresh pasta in no time for the next day.