in a bowl mix cream cheese mozzarella Parmesan sour cream mayonnaise spinach garlic green onions salt pepper and red pepper flakes until evenly combined.
Assemble
Using a serrated knife cut the loaf into a crosshatch pattern making 1 inch cubes without cutting through the bottom crust
gently pull apart the cuts and spoon the spinach mixture deep into the gaps
brush the top and exposed edges with melted butter.
Bake
Wrap loaf loosely in foil and bake 15 minutes
uncover and bake 10 minutes until cheese is bubbling and top is lightly browned
rest 5 minutes then garnish with parsley and serve warm by pulling pieces apart.
Notes
1. Use frozen spinach for best texture and squeeze very dry; swap sour cream for Greek yogurt for a lighter dip; add chopped artichoke hearts or cooked bacon for variation; rewarm leftovers at 350 F covered until hot