Begin by sautéing fresh spinach in a bit of olive oil over medium heat until wilted, about 3-4 minutes. If using frozen spinach, thaw and drain it well.

In a mixing bowl, combine the cooked spinach with ricotta cheese, half of the mozzarella, and a pinch of nutmeg. Stir until the filling is smooth and creamy, then set aside.

Roll out fresh pasta sheets on a lightly floured surface to about 1/8-inch thick, or prepare store-bought sheets according to package instructions.

Place a spoonful of the filling onto each pasta sheet, leave space for sealing. Fold over and press edges firmly to seal.

Bring a large pot of salted water to a gentle boil. Carefully add the stuffed pasta and cook for 3-5 minutes, or until they float to the surface.

Preheat oven to 375°F (190°C). Spread a layer of marinara sauce in a baking dish, arrange pasta on top, drizzle with more sauce, and sprinkle remaining mozzarella and Parmesan.

Bake for 20 minutes, until cheese is bubbly and golden. Garnish with fresh basil and serve warm.