Question: Can burgers be only made with beef?
About the article "Hamburger", section "Variations".

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The menu consists of burgers made with organic meat, fresh cut french fries cooked in olive oil, a burger that can be made with as many as 10 patties ("vertigo" burger), two kinds of veggie burgers and hand-blended milkshakes.
The meat for non-vegetarian burgers is USDA-certified organic, grass fed, free range beef and the cheese is 6 month aged cheddar.
The beef is cooked on griddles heated by steam, rather than gas flame, for ensuring a more uniform surface temperature and faster temperature recovery.
The veggie burgers are cooked in a conveyor, keeping them away from the griddle where beef is cooked.
The fresh french fries are cooked in olive oil, after a process patented by Hans Hess.
The milkshakes are made from hand-scooped ice cream. 
Rice burgers, mentioned above, are also available in several East Asian countries such as Taiwan and South Korea.
Lotteria is a big hamburger franchise in Japan owned by the South Korean Lotte group, with outlets also in China, South Korea, Vietnam, and Taiwan.
In addition to selling beef hamburgers, they also have hamburgers made from squid, pork, tofu, and shrimp.
Variations available in South Korea include Bulgogi burgers and Kimchi burgers.
In the Philippines a wide range of major U.S. fast-food franchises are well represented, together with local imitators, often amended to the local palate.
The chain McDonald's (locally nicknamed "McDo") have a range of burger and chicken dishes often accompanied by plain steamed rice and/or French fries.
The Philippines boasts its own burger-chain called Jollibee, which offers burger meals and chicken, including a signature burger called "Champ".
Jollibee now has a number of outlets in the United States, the Middle East and East Asia.
In India, burgers are usually made from chicken or vegetable patties due to cultural beliefs against eating beef (which stem from Hindu religious practice) and pork (which stems from Islamic religious practice).
Because of this, the majority of fast food chains and restaurants in India do not serve beef.
McDonald's in India, for instance, do not serve beef, offering the "Maharaja Mac" instead of the Big Mac, substituting the beef patties with chicken.
Another version of the Indian vegetarian burger is the Wada Pav consisting deep-fried potato patty dipped in gramflour batter.
It is usually served with mint chutney and fried green chili.
In Pakistan, apart from American fast food chains, burgers can be found in stalls near shopping areas, the best known being the "shami burger".
This is made from "shami kebab", made by mixing lentil and minced lamb.
Onions, scrambled egg and ketchup are the most may be toppings.
In Malaysia there are 300 McDonald's restaurants.
The menu in Malaysia also includes eggs and fried chicken on top of the regular burgers.
Burgers are also easily found at nearby mobile kiosks, especially Ramly Burger.
In Mongolia, a recent fast food craze due to the sudden influx of foreign influence has led to the prominence of the hamburger.
Specialized fast food restaurants serving to Mongolian tastes have sprung up and seen great success.
In Turkey, in addition to the internationally-familiar offerings, numerous localized variants of the hamburger may be found, such as the Islak Burger (lit.
"Wet-Burger"), which a beef slider doused in seasoned tomato sauce and steamed inside a special glass chamber, and has its origins in the Turkish fast food retailer Kizilkayalar.
Other variations include lamb-burgers and offal-burgers, which are offered by local fast food businesses and global chains alike, such as McDonald's and Burger King.
Most burger shops have also adopted a pizzaria-like approach when it comes to home delivery, and almost all major fast food chains deliver. 
Hamburgers in the UK and Ireland are very similar to their US cousins, and the High Street is dominated by the same big two chains as in the U.S. — McDonald's and Burger King.
The menus offered to both countries are virtually identical, although portion sizes tend to be smaller in the UK.
In Ireland the food outlet Supermacs is widespread throughout the country serving burgers as part of its menu.
In Ireland, Abrakebabra (started out selling kebabs) and Eddie Rocket's are also major chains.
An original and indigenous rival to the big two U.S. giants was the quintessentially British fast-food chain Wimpy, originally known as Wimpy Bar (opened 1954 at the Lyon’s Corner House in Coventry Street London), which served its hamburgers on a plate with British-style chips, accompanied by cutlery and delivered to the customer's table.
In the late 1970s, to compete with McDonald's, Wimpy began to open American-style counter-service restaurants and the brand disappeared from many UK high streets when those restaurants were re-branded as Burger Kings between 1989–90 by the then-owner of both brands, Grand Metropolitan.
A management buyout in 1990 split the brands again and now Wimpy table-service restaurants can still be found in many town centers whilst new counter-service Wimpys are now often found at motorway service stations.
Hamburgers are also available from mobile kiosks, particularly at outdoor events such as football matches.
Burgers from this type of outlet are usually served without any form of salad — only fried onions and a choice of tomato ketchup, mustard or brown sauce.
Chip shops, particularly in the West Midlands, North-East, Scotland and Ireland, serve battered hamburgers called batter burgers.
This is where the burger patty, by itself, is deep-fat-fried in batter and is usually served with chips.
Hamburgers and veggie burgers served with chips and salad, are standard pub grub menu items.
Many pubs specialize in "gourmet" burgers.
These are usually high quality minced steak patties, topped with items such as blue cheese, brie, avocado et cetera.
Some British pubs serve burger patties made from more exotic meats including venison burgers (sometimes nicknamed Bambi Burgers), bison burgers, ostrich burgers and in some Australian themed pubs even kangaroo burgers can be purchased.
These burgers are served in a similar way to the traditional hamburger but are sometimes served with a different sauce including redcurrant sauce, mint sauce and plum sauce.
In the early 21st century "premium" hamburger chain and independent restaurants have arisen, selling burgers produced from meat stated to be of high quality and often organic, usually served to eat on the premises rather than to take away.
Chains include Gourmet Burger Kitchen, Ultimate Burger, Hamburger Union and Byron Hamburgers in London.
Independent restaurants such as Meatmarket and Dirty Burger developed a style of rich, juicy burger in 2012 which is known as a "dirty burger" or "third-wave burger".
In recent years Rustlers has sold pre-cooked hamburgers re-heat able in a microwave oven in the United Kingdom.
In the UK, as in North America and Japan, the term "burger" can refer simply to the patty, be it beef, some other kind of meat, or vegetarian. 
A patty, in American, Australian and New Zealand English, is a flattened, usually round, serving of ground meat or meat alternatives.
The meat is compacted and shaped, cooked, and served.
Patties can be eaten with a knife and a fork in dishes like Salisbury steak, but are typically served in a sort of sandwich called a "burger", or a hamburger if the patty is made from ground beef.
The patty itself can also be called a burger, whether or not it is served in a sandwich, especially in the United Kingdom and Ireland, where the term "patty" is rarely used.
Similar-shaped meat cakes not made from ground beef may also be called "burger": "turkey burgers" or "fishburgers" may be made from reshaped mechanically separated meat.
Sometimes burgers are breaded.
Veggie burger patties are made without animal products.
In Ireland, traditional chippers often serve batter burger (a beef-based patty dipped in batter and deep fried) or spice burger (a savory patty made with a proprietary recipe of meats and spices).
These are served in a greaseproof paper bag and eaten with the hands. 
The Fryer’s Chargrilled Burgers are grilled hamburgers made on real charcoal grill with 100% pure beef, American Cheese Lettuce, Tomato and other vegetables.
Fryer’s uses buns that are softer and "eggier" than normal buns.