PREHEAT manufacturer's recommended amount of vegetable oil in deep-fryer to 365°F (OR) preheat enough fat to onion rings in a deep heavy stovetop pot to 365°F (use a heat-safe thermometer to gauge).
PEEL then slice 2 large sweet onions into 1/3-1/2 inch rings (you may use all of onion, or just the larger outer rings).
INTO a medium bowl add 1 cup self-rising flour, 1 1/2 tablespoons prepared Recipe #453973, 2 teaspoons granulated sugar, and 1/2 teaspoon salt; MIX ingredients well; WHISK in 1 cup cold water and 1 egg until combined well, without over-mixing.
ADD 1/3 cup all-purpose flour into a small bowl for the DREDGE; FILL another small bowl with 1/2 cup panko breadcrumbs (optional) if a panko breading is desired for the final coating.
TOSS a few onion slices in the flour DREDGE until lightly coated.
DIP a few floured onions into the BATTER; REMOVE rings one at a time using a fork or skewer, until 3 or four are battered.
LIGHTLY coat onion rings in panko breadcrumbs, if using, lifting once again onto the fork/skewer.
TILT battered/breaded onion rings off the skewer, onto the surface of hot oil; SHAKE fryer basket gently to prevent onion rings from sinking and sticking (which they inevitably do sometimes).
TURN onion rings once, using the skewer, when light golden on the underside; CONTINUE frying just until light golden brown on both sides (don't overcook!); REPEAT with remaining onion rings.
SEASON with a light sprinkle of salt if desired; SERVE with your favorite condiments and ENJOY!