Also works great as a bread stick dipping sauce!
Heat the butter in a saucepan over a low heat. Cook the spinach in there until it's warmed, about 1 minute. Add in cream and cream cheese and continue cooking and stirring until the cream cheese is melted, about 5 minutes.
Fold the Parmesan and garlic powder into mix and season with your preference of salt and pepper. Let it simmer until the sauce has thickened and becomes smooth, about 10 more minutes.