Place the frozen spinach in a microwave-safe bowl. Cover and microwave on high just until thawed, about 4 minutes. Place the spinach in a colander and press on it to get out as much liquid as possible.
In a medium saucepan, melt the butter over medium heat. Add the garlic and cook for 1 minute.
Stir in the spinach, salt, pepper, nutmeg, heavy cream and Parmesan. Cook, stirring, just until heated through, 1-2 minutes, then serve.
If the spinach seems dry, you can add up to ¼ cup additional heavy cream. You can also add plain unsweetened almond milk.