In a separate bowl whisk together the egg and heavy cream and toss the sliced onion in the mixture until fully coated.
One at a time, toss the coated onion rings in the breading mixture.
In a large frying pan heat about 1 cup of bacon grease or other frying fat on medium heat just until it begins to smoke.
Cook breaded onion rings for 1-2 minutes per side in the hot oil until as brown as desired.
Airfryer instructions: Place breaded onion rings in the airfryer basket in a single layer and spray lightly with cooking spray or drizzle with a bit of melted bacon grease or ghee. Cook at 400 degrees for about 8 minutes, flipping halfway through.
This recipe would also work well in a deep fryer. Refer to your deep fryer's instructions.