How to Make It
In a large bowl, combine the onions with the milk and stir to coat. Cover and refrigerate for 2 hours.
In a medium bowl, whisk the flour with the paprika and celery salt. Drain the onions very well in a colander, then set the colander over a large bowl. Sprinkle the flour mixture over the onions and toss with your hands to evenly coat. Shake well to remove any excess flour.
In a large saucepan, heat the oil to 350°. In about 5 batches, fry the onions over moderate heat until golden brown, about 2 minutes per batch. Using a slotted spoon, transfer the onions to paper towels to drain; season lightly with salt. Return the oil to 350° between batches. Serve hot.