For the sauce: In a small bowl combine the mayonnaise, chives, parsley, cornichons, capers and lemon juice. Mix until smooth and taste for seasoning; adjust the flavors if needed. Transfer to a small ramekin.
For the fish and chips: Combine the rice flour, all-purpose flour, baking powder and salt, and whisk in enough of the club soda to reach the consistency of a thick batter.
Pour the oil in a large saucepot set over medium-high heat, and heat until a deep-frying thermometer inserted in the oil reaches 350 degrees F.
Dip a piece of the fish into the batter, and then slowly lower into the hot oil. Repeat with the second piece of fish. Cook until golden brown and flaky, 4 to 6 minutes. Use a slotted spoon to remove the fish, and place on a paper-towel-lined plate to absorb any excess oil. Season with salt immediately, and then transfer to serving plates. Serve the fish with the tartar sauce, French fries and lemon wedges.