Cook the Aromatics: In a large skillet or saucepan, melt the butter over medium heat. Add the chopped onion and cook for 3-4 minutes until softened. Add the minced garlic, nutmeg (if using), and black pepper. Cook for another minute until fragrant.

1. Add the Cream and Cheese: Pour in the heavy cream and milk, stirring to combine. Let it simmer gently for 3-4 minutes, allowing the mixture to thicken slightly. Add the grated Parmesan cheese and cream cheese, stirring until the cheese is fully melted and the sauce becomes smooth and creamy.
2. Cook the Spinach: Gradually add the spinach to the skillet, stirring frequently. Add a handful at a time, letting the spinach wilt down before adding more. Continue until all the spinach is added. Cook for an additional 3-5 minutes, stirring occasionally, until the spinach is fully wilted and tender.
3. Season and Serve: Taste the creamed spinach and adjust the seasoning with salt and more black pepper as needed. Serve the creamed spinach warm as a side dish.