Step 1: Preheat your oven to 375°F (190°C). Grease a 9-inch pie dish or a small (approx. 8x8 inch) baking dish with olive oil or butter.
Step 2: If using fresh spinach, heat a large pan over medium heat with a tablespoon of olive oil. Add the spinach and cook until wilted, about 2-3 minutes. Transfer to a colander and, once cool enough to handle, squeeze out as much liquid as possible. If using frozen spinach, thaw it completely and squeeze very dry.
Step 3: In a large mixing bowl, combine the whole milk ricotta, eggs, grated Parmesan cheese, finely chopped fresh basil, fresh parsley, and dried oregano.
Step 4: Add the thoroughly drained spinach to the ricotta mixture. Season generously with salt, black pepper, and a pinch of nutmeg.
Step 5: Gently fold all the ingredients together until just combined. Be careful not to overmix.
Step 6: Pour the ricotta mixture into your prepared baking dish. Use a spatula to smooth the top.
Step 7: Bake for 40-50 minutes, or until the top is golden brown and the edges are set. The center should still have a slight jiggle.
Step 8: Once baked, remove the dish from the oven and let it rest for 10-15 minutes before serving. Garnish with a few fresh basil leaves or a sprinkle of additional Parmesan if desired.