Cook spinach in microwave. Place in colander to drip and cool. Once cool, squeeze handfuls of spinach over sink to remove as much water as possible. Use papertowels to help pat dry. Set aside Sauté onion in butter until tender. Remove from cooktop. Stir in spinach and let set a few minutes to allow spinach to soak in the butter. In a very large mixing bowl, beat cream on medium speed and gradually add in the cream cheese until if forms a creamy mixture. Add remaining ingredients into the mixing bowl, except the Parmesan cheese, and mix together. Let chill for at least 2 hours. When ready to serve, spoon mixture into microwave safe serving bowl and top the mixture with Parmesan cheese. Microwave until hot (approximately 5 to 7 minutes) stirring mixture every few minutes.