Line a fine-mesh strainer with cheesecloth, add ricotta, and refrigerate overnight to drain excess moisture.
Mound flour on a work surface, create a well, add eggs, olive oil, and salt. Beat eggs with a fork, gradually incorporating flour until a shaggy dough forms. Knead for 8-10 minutes until smooth, then wrap and rest for 30 minutes.
In a bowl, combine drained ricotta, Parmesan, egg yolk, basil, salt, pepper, and optional nutmeg until smooth. Refrigerate until ready to use.
Divide rested dough into 4 pieces. Roll one piece through a pasta machine, starting at the widest setting and folding a few times, then progressively narrow to setting 6 (Marcato) or 7 (KitchenAid) until thin enough to see your hand's shadow through it.
Place heaping tablespoons of filling on one half of a pasta sheet, 1.5 inches apart. Brush exposed dough with egg wash, fold the sheet over, and press out air to seal. Cut into individual ravioli with a fluted pastry wheel and transfer to a parchment-lined baking sheet dusted with semolina.
Bring a large pot of salted water to a gentle boil. Cook ravioli in batches of 8-10 until they float (2-3 minutes), then cook 2-3 minutes more until tender. Remove with a slotted spoon.
Toss hot ravioli with your chosen sauce, drizzle with olive oil or melted butter, and garnish with fresh Parmesan and basil. Serve immediately.