Beat the egg in a large mixing bowl. Add the club soda, flour, cornstarch, Essence, and salt and whisk until smooth. Cover and refrigerate for 30 minutes to 1 hour.
Pour enough oil into a large heavy pot or electric deep fryer to come halfway up the sides and heat to 360?F.
In batches, dip the crab claws into the batter and deep-fry until golden brown, 2 to 3 minutes. Using a slotted spoon, transfer the claws to paper towels to drain.
Serve immediately with the tartar sauce.
Yield: 4 servings