Onion Rings

In a heavy bottomed pot filled 3/4 of the way with vegetable oil, bring the temperature to 365 degrees F. Separate the onion slices into rings. In a medium size bowl, whisk together the flour, baking soda and baking powder. Dredge the onion rings in the flour mixture and shake off excess. Set aside. In a mixing bowl, whisk the egg yolk and then slowly pour in the soda water. Whisk until the batter is a smooth consistency. Dip the onion rings in the batter, working in batches. Deep fry a few of the rings at a time for 2 to 3 minutes, or until golden brown. Remove to a paper towel to drain. Season with salt immediately and serve while still hot.