There are a few types of onion ring batter, some of which result in a thick crust and others that just barely coat the onion. One of the most popular is a beer-based onion ring batter that uses beer as a leavening agent. A more basic flour and egg dough can be used to provide a smooth, thick coating. A Japanese-style tempura batter gives onion rings a light but crisp shell that allows the taste of the onion to come through clearly. Onion rings also can be dredged through flour, eggs and bread crumbs to create a thick, bready coating that will brown when baked or deep fried.
The simplest type of onion ring batter can be made from flour, an egg, baking powder and a little milk. Once the ingredients are combined into a smooth batter, each onion ring can be dipped, allowed to drain for a moment to remove any excess batter, and then dipped in hot oil or fried in a shallow layer of oil. The batter will create a smooth coating that can be thick around the onion rings, or the batter can be thinned out with more milk to make a lighter coating.
A beer batter is a popular type of onion ring batter. This is made from basic flour and eggs, although beer also is added. Once the ingredients are mixed together, the batter is allowed to sit in a refrigerator for a few hours until the beer starts to leaven the mixture. The coating this creates after deep frying is light with a subtle malt-like taste that complements the onion.
Tempura batter uses ingredients similar to those in the other types of onion ring batter, but the technique used is slightly different. The flour is first sifted until it is very fine in texture, or special tempura flour can be used. Ice water is added to the flour and mixed together, sometimes with cornstarch or baking powder and baking soda. Cold carbonated water or beer sometimes is used in place of ice water. After being deep fried, a tempura batter yields onions rings that have a very light and flaky coating that sometimes just barely coats the rings, allowing more of the onion flavor to come through.
Onions rings can be breaded for a robust coating. This involves first running each onion ring through some dry flour. The rings are dipped into eggs that have been whisked until well blended. As a last step, the onion rings are rolled in breadcrumbs and then deep fried. An even thicker coating can be made by dipping the rings in the flour a second time after placing them in the egg, and then back into the egg again before breading and deep frying.
