You can make this crunchy, salty, sweet-ish, treat in batches and keep them warm in the oven. There are a million and one ways to serve onion strings!!
1 large sweet onion (I like Vidalia's)
1 cup buttermilk
1 cup flour
1/2 teaspoon salt
1/2 teaspoon black pepper
1/4 teaspoon cayenne pepper
Peel the onion and slice it as thin as you can. A mandolin works well here, but I don't have one, so I just slice the onion as thin as I can.
Soak the onion slices in the buttermilk for about an hour, making sure you press the slices down into the liquid. When I'm in a hurry, I've done this step in 1/2 hour and they turned out great.
In another bowl, mix the flour, salt, pepper and cayenne and set aside. Heat a quart of vegetable oil to 375F.
Using tongs, remove a handful of onion slices from the buttermilk and put them into the flour. Toss around gently to coat.
With the tongs, take the slices out of the flour and tap the tongs on the edge of the bowl to remove excess flour from the onion pieces.
Put the floured slices into the hot oil and stir gently to separate the slices. These will be golden brown in a minute or so, so watch them carefully.
Drain on paper towels and salt them to taste. Repeat batches until all onion strings are cooked.