Mound the flour on a clean surface and create a wide well in the center. Crack eggs into the well and add olive oil and salt. Beat eggs gently with a fork, gradually incorporating flour from the inner walls.
Knead the dough for 8-10 minutes until smooth and elastic. Form into a ball, wrap in plastic, and let rest at room temperature for 30 minutes.
Line a fine-mesh strainer with cheesecloth. Place ricotta in the strainer over a bowl and refrigerate for at least 2 hours to drain excess liquid.
Transfer drained ricotta to a bowl. Add Parmesan, egg yolk, nutmeg, salt, pepper, and optional basil. Mix thoroughly, then cover and refrigerate until ready to use.
Cut rested dough into 4 equal pieces. Roll each piece through a pasta machine, starting at the widest setting and gradually decreasing until you reach setting 6 or 7, until you can see your hand through the dough.
Lay one pasta sheet on a floured surface. Place small mounds (about 1 teaspoon) of filling 2 inches apart, leaving a 1-inch border. Brush beaten egg wash between mounds and around edges.
Carefully drape a second pasta sheet over the filling. Press gently around each mound to remove air pockets. Use your fingers to seal the sheets together firmly.
Use a ravioli cutter or sharp knife to cut between the mounds. Press the tines of a fork around all edges to reinforce the seal. Place finished ravioli on a semolina-dusted baking sheet.
Bring a large pot of salted water to a rolling boil. Gently lower ravioli into the water a few at a time, avoiding overcrowding. Cook for 3-4 minutes after they float to the surface.