Mix in a bowl the dry ingredients (flour, corn starch, instant mashed potatoes and the cayenne). Pour the soda into the bowl and stir well. Let it sit for at least 10 minutes.
Put the breadcrumbs in a shallow pan to be ready. Cut the onions (if you haven't already) 1/4-inch but not any thicker otherwise they won't cook. Carefully separate them to rings.
Dub in the bowl a few rings at a time, pull them out with a fork and sink them in the breadcrumbs.Remove them carefully one at a time and place them right in the frying pan.
Oil's temperature must be 350 F. Fry them until golden brown (about 3 minutes).
When ready salt them well. Turn off the heat. Serve them to a plate. Take a fork. Open your mouth. Use the fork to transport food from the plate into your mouth. Enjoy! :)