Lightly grease a 9×13-inch baking dish with non-stick spray.

Season both sides of the chicken with salt and pepper, and lightly coat each side with flour.

Heat 2 tablespoons of butter in a large skillet over medium heat. Cook the chicken for 3-5 minutes per side (use 3 minutes for cutlets and 5 minutes for full chicken breasts) until golden brown.

Transfer the cooked chicken to a plate, covering it with foil to keep warm.

In the same skillet, melt the remaining 2 tablespoons of butter. Sauté the onions for 4 minutes, then add the garlic and cook for another minute.

Add wine (or broth) to the pan, stirring to scrape up the browned bits at the bottom. Bring it to a boil, reducing the liquid by half. Stir in the cream, bring to a boil again, and reduce by half.

Add fresh spinach and any juices from the chicken, cooking until the spinach wilts.

Let the sauce simmer until it thickens again. Adjust seasoning to taste, and preheat the broiler.

Arrange the cooked chicken in the baking dish. Top with the spinach sauce and evenly sprinkle mozzarella cheese over the chicken.

Broil for a few minutes until the cheese is melted and golden. Garnish with nutmeg and parsley before serving.