Preheat the oven to 340°F (170°C). Sauté the cooked spinach in a small amount of butter, then remove from heat and add grated Parmesan cheese.

Mix well and fill the cocotte, spreading the spinach more along the sides than in the center. Pour the egg white into the center and bake for 10 to 12 minutes, until the white is set.

After that time, add the yolk on top of the white and return to the oven for another 3 minutes. Remove the cocotte and sprinkle with salt and pepper.