Modern pizza was invented in Naples, and the dish and its variants have since become popular in many countries. Another variation is grilled pizza, created by taking a fairly thin, round (more typically, irregularly shaped) sheet of yeasted pizza dough, placing it directly over the fire of a grill, and then turning it over once the bottom has baked and placing a thin layer of toppings on the baked side.  During this time, some people observe National Pizza Month by consuming various types of pizzas or pizza slices, or going to various pizzerias. ", "The Grilled Pizza Margarita at Al Forno in Providence", "Providence Featured on Travel Channel's Man V. Food Nation", "La historia de la pizza argentina: ¿de dónde salió la media masa? After this, it is typically left undisturbed and allowed time to proof. , The world's most expensive pizza listed by Guinness World Records is a commercially available thin-crust pizza at Maze restaurant in London, United Kingdom, which costs GB£100.  Pizza chains such as Domino's Pizza, Pizza Hut, and Papa John's, pizzas from take and bake pizzerias, and chilled or frozen pizzas from supermarkets make pizza readily available nationwide. ), which is then baked at a high temperature, traditionally in a wood-fired oven. With mass production of pizza, the process can be completely automated. A wrapped, mass-produced frozen pizza to be cooked at home. , Grilled pizza was offered in the United States at the Al Forno restaurant in Providence, Rhode Island by owners Johanne Killeen and George Germon in 1980. For the restaurant chain, see, Usually savory dish of flattened bread and toppings, "Pizza, A Slice of American History" Liz Barrett (2014), p.13, "The Science of Bakery Products" W. P. Edwards (2007), p.199. The pizza was named "Ottavia" in homage to the first Roman emperor Octavian Augustus, and was made with a gluten-free base. , There are several instances of more expensive pizzas, such as the GB£4,200 "Pizza Royale 007" at Haggis restaurant in Glasgow, Scotland, which is topped with caviar, lobster, and 24-carat gold dust, and the US$1,000 caviar pizza made by Nino's Bellissima pizzeria in New York City, New York.  Ricotta is a common type of cheese used on white pizza in the United States. The traditional style of grilled pizza employed at Al Forno restaurant uses a dough coated with olive oil, strained tomato sauce, thin slices of fresh mozzarella, and a garnish made from shaved scallions, and is served uncut. This quest to create the ideal and economical pizza cheese has involved many studies and experiments analyzing the impact of vegetable oil, manufacturing and culture processes, denatured whey proteins, and other changes in manufacture. Helga Rosemann, Flammkuchen: Ein Streifzug durch das Land der Flammkuchen mit vielen Rezepten und Anregungen (Offenbach: Höma-Verlag, 2009).  Many companies sell ready-baked frozen pizzas to be reheated in an ordinary home oven. In the 6th century BC, the Persian soldiers of Achaemenid Empire during the rule King Darius I baked flatbreads with cheese and dates on top of their battle shields and the ancient Greeks supplemented their bread with oils, herbs, and cheese. Standard Argentine pizza has a thicker crust, called "media masa" (half dough) than traditional Italian style pizza and includes more cheese.  Garlic, herbs, or other ingredients are sometimes added to the pizza or the crust to maximize the flavor of the dish. Some grocery stores sell fresh dough along with sauce and basic ingredients, to complete at home before baking in an oven. Houghton Mifflin Harcourt.  A small pizza is sometimes called a pizzetta. Methods have been developed to overcome challenges such as preventing the sauce from combining with the dough and producing a crust that can be frozen and reheated without becoming rigid.  There are concerns about negative health effects. It is traditionally plain, but may also be seasoned with garlic or herbs, or stuffed with cheese.