Turn oven to 350°F so it can heat up.
In a large skillet over medium heat, saute the onion, pepper, and garlic in the oil until the veggies are softened.
Stir in the spinach, pesto, Worcestershire, paprika, salt, pepper, and mayo.
Reduce the heat to low, and add the cream cheese, sour cream, parmesan, and cheddar cheese. Stir until it's melty. Remove from heat.
Hollow out the French bread so that it's like a long bowl or trough.
Pour the cheesy spinach mixture into the hollowed out bread and spread it evenly.
Sprinkle the mozzarella cheese on top.
Bake in the preheated oven for 25 minutes.
Serve with the bread that was removed from the French loaf and crackers.