Step 1

Make the sauce: In a small serving bowl, stir together the mayonnaise, pickles, cilantro, hoisin, onion, fish sauce, salt, and white pepper. Cover and refrigerate until ready to use.

Step 2

Make the fish: In a large bowl, whisk together the all-purpose flour, rice flour, corn flour, baking powder, five-spice, salt, and sugar. Add the club soda and whisk until smooth.

Step 3

To a large pot or Dutch oven set over medium-high heat and fitted with a deep-fry thermometer, add the oil to a depth of 1½ inches. While the oil heats, pat the fish dry with paper towels and season generously with salt and white pepper. In a shallow bowl, place the cornstarch, then add the fillets and turn to coat. When the temperature reads 350ºF, dredge half of the fillets in the batter, allowing any excess to drip back into the bowl. Gently lower into the oil and fry, turning halfway through cooking, until the batter is puffed and golden brown, 6–8 minutes total. Transfer to a rack set over a paper-towel-lined baking sheet and season with flaky salt and white pepper. Repeat with the remaining fish.

Step 4

To serve, transfer the fish to a platter and garnish with the cilantro and sliced chile. Serve immediately with the tartar sauce on the side.