Thaw and drain the frozen spinach. If it’s not already chopped then finely chop. Drain the artichoke hearts and cut into small pieces. Minced the garlic. In a large bowl, combine the spinach, artichoke hearts, softened cream cheese, mayonnaise, sour cream, half the parmesan cheese, garlic and crushed chili flakes. Season with salt and pepper. Mix until the entire mixture is evenly moist. Pour the mixture into an eight inch cast iron skillet, square pan or pie dish.