-sliced 1/4-in thick Oil for deep frying MIX THE FLOUR, SALT, PEPPER, oil and yolks together. Gradually whisk in the beer. Refrigerate the batter 3 1/2 hours to rest before using. Slice onions, and dip them in the batter. Deep-fry in 375F oil until golden brown. This batter also works well on other vegetables besides onion rings--and it's great on fish, too.