01 - Melt butter in a large skillet over medium heat. Add chopped onion and cook for 2 to 3 minutes until translucent.
02 - Incorporate minced garlic into the skillet and cook for 30 seconds until fragrant.
03 - Add spinach in batches, stirring continuously until wilted and reduced in volume.
04 - Reduce heat to low. Stir in cream cheese, heavy cream, and Parmesan cheese until fully melted and sauce is smooth.
05 - Add nutmeg, salt, and black pepper. Simmer gently for 3 to 4 minutes, stirring often until slightly thickened.
06 - Taste and adjust seasonings if needed. Serve warm as a side dish or vegetarian main.