Okonomiyaki is a pan-fried Japanese dish cooked with various ingredients. Okonomi means "what you like" or "what you want", and yaki means "grilled" or "cooked". Thus, the name of this dish means "cook what you like, the way you like". In Japan, okonomiyaki is usually associated with the Kansai or Hiroshima areas, but is widely available throughout the country. Toppings and batters tend to vary according to region.
Kansai (Osaka)-style okonomiyaki is a pan-fried batter cake. This is the style of okonomiyaki found throughout most of Japan. The batter is made of flour, grated yam, water or dashi, eggs and shredded cabbage, and usually contains other ingredients such as green onion, meat (generally pork or bacon), octopus, squid, shrimp, vegetables, kimchi, mochi or cheese. Okonomiyaki is often oddly compared to an omelette, pizza, or pancake, and as such is sometimes referred to as "Japanese pizza" or as "Japanese pancake", though as unique as those foods are, so is okonomiyaki. Many okonomiyaki restaurants are set up as grill-it-yourself establishments, where the server produces a bowl of raw ingredients that the customer mixes and grills at tables fitted with special hot plates. They may also have a diner style counter where the cook will prepare the dish right in front of you.
In Osaka (the largest city in the Kansai region), where the dish is said to have originated, okonomiyaki is prepared much like a pancake. The batter and other ingredients are fried on both sides on either a hot plate (teppan) or a pan using metal spatulas that are later used to slice the dish when it has finished cooking. Cooked okonomiyaki is topped with ingredients that include okonomiyaki sauce (similar to Worcestershire sauce but thicker and sweeter), nori, fish flakes, Japanese mayonnaise and ginger. When this style of okonomiyaki is served with sliced cabbage and a layer of fried noodles (either ramen or udon worked into the mix) it is called modanyaki (modern yaki). Negiyaki is a thinner offshoot of okonomiyaki made with a great deal of Welsh onion.
In Hiroshima, the ingredients are layered rather than mixed together. The layers are typically batter, cabbage, pork, optional items (squid, octopus, cheese, etc.), noodles (soba, udon) topped with a fried egg and a generous dollop of okonomiyaki sauce. The amount of cabbage used is usually 3 - 4 times the amount of Osaka style. It starts out piled very high and is generally pushed down as the cabbage cooks. The order of the layers may vary slightly depending on the chef's style and preference, and ingredients will vary depending on the preference of the customer. People from Hiroshima tend to claim that this is the correct way to make okonomiyaki.