Heat butter and oil, then sauté onion until aromatic and translucent, then add in the spinach.
Add cream cheese and quick melting cheese; continue sautéing until cheese melts.
Transfer the cheesy creamed spinach into an 8-inch square baking dish.
Sprinkle grated mozzarella on top of the spinach. Set aside.
In a separate bowl, mix all-purpose flour, bread crumbs, melted butter, and parmesan cheese. Mix well.
Sprinkle the flour-bread crumbs mixture on top of the spinach; make sure that the flour-bread crumbs mixture covers the top of the cheesy creamed spinach.
Bake the cheesy creamed spinach until the flour-bread crumbs mixture turns brown.
Remove the cheesy creamed spinach from the oven and Serve.