Cook spinach according to package instructions then place in a clean tea towel. Set the spinach (in the towel) over a sieve in the sink. Squeeze as much water out of the spinach as possible, then set aside.

In a large sauté pan, add butter and set over medium heat. Once melted, add onion and cook for 4 to 5 minutes, or until the onions are translucent and are beginning to soften.

Add spinach, milk, Parmesan cheese and cream cheese to the skillet and mix to combine. Bring the mixture to a gentle simmer and cook for 2 to 3 minutes, or until the milk has thickened slightly.

Season with salt, pepper and nutmeg and serve warm.