* 2 large yellow onions, peeled, sliced into 1/2-inch to 3/4-inch thick ringed slices, rings separated
* 2 cups buttermilk, or 1 cup plain yogurt mixed with 1 cup milk
* Freshly ground black pepper
* 1 1/4 cups all-purpose flour and 1/4 cup cornmeal OR 1 cup prepared cornbread flour plus 1/2 cup all-purpose flour
* 2 or 3 cups of grapeseed oil, or other high smoke-point oil such as canola oil or peanut oil
Equipment needed: a 5-quart heavy-bottomed dutch oven, tongs, candy thermometer, paper towels, cookie sheets
1 Combine the buttermilk (or yogurt and milk) with 1 1/2 teaspoons salt and 1 teaspoon black pepper in a large bowl. Add the onions to the buttermilk mixture and coat thoroughly. Let sit at least 15 minutes.
2 In a separate bowl combine the flour and cornmeal, 1 teaspoon of salt and 1/2 teaspoon of pepper. Set aside.
3 Add the oil to a largish Dutch oven pan - about 5-quart or 6 quart size. Make sure that the pan is absolutely dry inside before you add the oil. Any water droplets in the pan will cause the oil to splatter violently as it heats up. The oil should create a layer anywhere from 3/4-inch to an inch thick. Use more oil if necessary. Heat the oil to 350°F. Use a candy thermometer to measure the heat of the oil. You may need to tilt the pan in order to cover the thermometer's sensor completely and get an accurate reading. I have found some instant-read thermometers to be useless for this purpose as their sensors are 2 1/2 inches up from the bottom. A good old fashioned metal-encased thermometer works best.
You can test if the oil is ready by moistening a little bit of the flour and dropping it in the pan. If it sizzles and fries, it's ready. If it burns, take the pan off the heat and let the oil cool down a bit.
4 Working in batches, lift some onion rings out of the buttermilk and coat them in the flour mixture. Use tongs to place them one by one in the hot oil. Fry for a minute on each side, until golden brown. Do not crowd them. Place finished onion rings on a cookie sheet lined with paper towels to absorb the excess oil. Keep the complete onion rings warm in a 200°F oven while you fry the rest. Between batches, if you end up needing more oil, add some. Let the temp get back up to 350°F before starting the next batch.Serve hot.