Preheat vegetable oil to 350 degrees. Add enough oil to fill the cooking container to 3 inches deep.
Peel onions, and cut into ½ to ¾ inch rings. Separate onions into rings. Take the center rings and save for another recipe. You can chop those small rings for chopped onions in another recipe.
Set up a breading station by placing three small bowls or dishes into a row. In the first shallow container add flour, seasoned salt, and black pepper, stir to combine. In the second dish combine the eggs with 1 cup of milk. Whisk the eggs and the milk together until they are well-combined. Finally, in the third container, add the panko breadcrumbs.
Breading the Onion Rings
First, dip the rings into the flour, and allow them to rest a couple of minutes on a wire rack. Then dip the floured onion ring into the egg wash mixture. Shake the onion ring gently to remove the excess egg wash, then place into the panko breadcrumbs. Coat the panko breadcrumbs over the onion ring well. Place the onion ring back onto a wire rack and allow it to rest a minute or two before cooking. This will help keep the coating in place.
Cooking the Onion Rings
Make sure you heat the oil to 350 degrees. You can use a deep fryer, or you can simply use a frying pan with 2 or 3 inches of oil in the frying pan. Cook for two to three minutes filling flipping half way through cooking. Remove onion ring and drain on a wire rack before serving.
Sometimes panko breadcrumbs aren't very uniform coming out of the package. You can place your panko crumbs into a plastic bag and gently roll a rolling pin over them to make them more uniform. The Panko crumbs will coat the onions better this way.