Preheat oven to 425 degrees F and place rack on top 3rd of the oven. Melt butter in an 8-inch cast iron skillet or oven safe pan. Saute garlic and onion until soft, about 2-3 minutes. Add shrimp, chili flakes and salt. Cook until shrimp turns pink, about 1-2 minutes. Add white wine and cook at a simmer until about 1 tablespoon liquid remains.
Remove from heat and stir in cream cheese, sour cream, mayonnaise, mozzarella cheese, 1/4 cup parmesan cheese, 2 tablespoons parsley and salt to taste. Top with remaining 1/4 cup parmesan cheese and place skillet into oven.
Bake for 18-20 minutes until cheese is bubbling. Increase heat to broil and cook until the top is browning in spots, about 3-5 minutes more. Remove from oven and top with 1 tablespoon chopped parsley.
Let rest 5 minutes before serving with toast or crackers and vegetable crudite.