Cook spinach according to package directions. Drain and set aside. Sauté chopped onion in butter until tender.
With a beater, beat whipping cream on medium speed and gradually fold in cream cheese until it forms a creamy mixture. Mix all remaining ingredients, except for the parmesan cheese, adding salt, peppers, onion and garlic powder (if you desire) to your taste preference.
Marinate in the refrigerator for at least two hours (the longer the better). Top dip with the shredded Parmesan cheese and heat individual portions in the microwave until it is hot and the cheese is melted. Serve with restaurant-style tortilla chips.