Whisk in more beer (about 1/2 cup) until the batter is smooth and creamy, about the consistency of pancake batter. Using tongs, dip an onion ring into the batter and flip to coat completely, shaking excess batter back into the bowl.
Stir in beer and egg white (batter will be thick). Heat 1 1/2 teaspoons oil in a large nonstick skillet over medium-high heat. Dip 5 onion rings in batter, letting excess drip off. Add onion rings to pan; cook for 2 minutes on each side or until golden.
Remove onion rings from buttermilk, shake off excess, dredge in flour, shake off excess, then dip in beer batter. Drop some onion rings in oil and continue process, being sure not to crowd rings as they will stick together.
Beer Battered Onion Rings have a super crispy and flavorful exterior. The onions are presoaked to tenderize them and give them extra flavor. Dip them in a curry-flavored dipping sauce for an amazing appetizer or game day food.
Pour the beer into the well and whisk until combined. Let rest, covered for 1 hour. Peel onions and cut crosswise 1/3 inch thick and separate into rings. Dust the onion rings with the additional flour, shaking off the excess, and coat them with the batter.