For fried onion rings, first peel onions and cut into thick rings. Mix rings with milk in a baking bowl. Empty oil 2 1/2 inches high into a deep frying pan or large pot and heat. Place a few handfuls of cornmeal in a paper or plastic bag.
When the oil reaches 175 °C, place a handful of onion rings in the bag, cover the opening and shake the bag well. Then put the floured onion rings into the hot oil and deep-fry for 3 minutes. Stir from time to time.
Once the fried onion rings are nice and crispy brown, scoop them out with a slotted spoon, drain on paper towels and sprinkle with salt.