The onion rings at Bessinger's, Robert's, and Melvin's are massive for two reasons. First, they use a large onion with thick layers. Then, they slice that big onion into wide rings. So, from the beginning, you have the makings of a jumbo onion ring. In addition, the batter they use expands considerably when cooked. Huge rings of onion with a fast-rising batter yield the enormous onion rings famous at Bessinger's.