2 Large onions
1/2 c. dark beer
1/2 c. club soda
1 tbsp. vegetable oil
1 egg white
1/2 tsp. cayenne pepper
1 tsp. kosher or sea salt
1 c. flour
1/4 tsp. mustard powder
1/2 tsp. onion powder
Pour beer and soda into food processor. Sprinkle in pepper, mustard, salt and onion powder and oil. Pulse until combined. Add flour last.
Whisk egg white until frothy in a shallow bowl. Gently stir in contents of food processor, mixing until combined.
Slice large onions into rings. Separate rings. Soak in a small amount of milk for 10 minutes. Drain and dip in batter.
Fry small batches in hot oil (365F), turning once, gently to brown evenly. Remove using a slotted spoon. Season with salt and pepper while still hot from fryer.
