Preheat oven to 400° F. In a large bowl, mix all three cheeses, and your mayonnaise. Stir in artichoke hearts and chopped spinach. Set aside.
Cut out the top of the loaf of bread to make a bowl, scoop out as much of the bread needed to make enough space for your spinach artichoke dip. Fill the bread bowl with the artichoke dip and place on a baking sheet. Top off with a little more mozzarella and Parmesan if desired.
Take the top section you cut out for the bread bowl and slice. Drizzle with a little olive oil and sprinkle with some Parmesan cheese, place on the pan with bread bowl. Cook for 20 minutes until everything is nice and melted. Enjoy!