Preheat oven to 350 degrees. In a large bowl, mix artichoke hearts, green onions, garlic, cream cheese, mayonnaise, sour cream, mozzarella and Parmigiano-Reggiano, reserving some of the cheese to sprinkle over the top.
Hollow 1/2 an inch out of the center of both halves of the bread. Spread the mixture into the hole in the bread slices and top with the reserved cheese. Place on a foil lined baking sheet.
Cover bread with foil and bake for 20 minutes. Remove the foil and turn the heat up to broil. Continue to cook for a few minutes more, until the cheese is melted and golden brown. Keep an eye on it, you don't want it to burn. Slice and Enjoy!