Peel and cut onions into 1 ⁄ 2-inch-thick slices.

Mix egg yolk, beer or carbonated water in a bowl.

Mix flour and baking powder into the liquid and whisk into a smooth batter. (Hint: Sift the flour).

Whip the egg white to soft peak and fold egg white into the batter.

Heat fryer or saucepan oil to 350 °F. (Use candy thermometer)

Coat the onion rings with flour and shake off excess.

Mix onion rings into the batter.

Quickly, one at a time, mix the onion ring from the batter, allow the excess mixture to drip off, and place into the hot oil, until golden brown.

Place on a plate lined with paper towel.

Season with salt and pepper and serve immediately.