In a large bowl, mix flour, cornstarch, salt, paprika and beer. Whisk well for about 2 minutes until a nice batter is formed. You'll want a nice smooth batter like pancake batter.
Heat oil in deep pan or pot to temperature of about 365 degrees F. Usually medium heat setting will do.
Dip onion slices into batter using tongs. Coat well and remove, shaking off excess batter and gently place in hot oil.
Cook in oil carefully turning every minutes or so for about 4-5 minutes or until golden brown.
Remove from oil and place on drain pan or plate with paper towels.