Separate the 1/4 inch slices of onion rings into separate rings.
Soak onion rings in a bowl of ice water for one hour, drain and pat dry with paper towels
In a small bowl combine flour, baking powder, and salt. Coat onion rings in the dry mixture and set aside.
In a medium bowl, whisk 1 egg and milk together until smooth
Heat oil in a deep-fryer or large saucepan to 375 degrees Fahrenheit or 190 degrees Celsius.
Dip flour-coated onion rings in the egg-milk mixture and place it on a wire rack to remove or let the excess egg-milk mixture drain.
When it is drained, pour bread crumbs in a shallow dish. Dip egg-milk coated onion rings into the bread crumbs until completely coated.
Fry the battered onion rings, working in batches, until golden brown for about 5 minutes. Transfer fried onion rings to a paper towel-lined plate using a slotted spoon (to let any excess oil drain off).
You can sprinkle each onion rings with a little salt.