In a large bowl, combine the egg yolks, salt, pepper and flour and whisk to combine. Gradually add the milk until the batter is smooth. Fold in the cheese and garlic and let rest 30 minutes.
Bring 2 quarts of water to a boil and add 1-tablespoon salt. Blanch the onions in the boiling water for 2 minutes, then refresh in ice water. Drain and pat dry with paper towels.
Fold the parsley into the batter. Beat the egg whites to stiff peaks and fold into the batter.
In a large, relatively tall-sided pan, heat the oil over high heat. Using tongs, dip each onion into the batter, shaking off the excess, then fry in the hot oil until golden brown on all sides. Remove with a slotted spoon or spider, drain on a plate lined with paper towels and season with salt. Serve hot.
Recipe copyright 2000, Mario Batali. All Rights Reserved.