Make celery root remoulade slaw: Roughly chop ⅓ cup capers and add to a small bowl, along with ⅓ cup mayonnaise, 2 tablespoons yuzu juice, and 1 heaping teaspoon dijon mustard. Mix to combine and add hot sauce, salt, and pepper to taste. If you crave more zip, add even more yuzu (or lime, if you’re substituting).
Peel and chop the celery root: Using a sharp knife, trim the top and bottom ¼-inch off of a 1 pound bulb celery root and place it cut-side down on a cutting board. Cut down and around the bulb to remove the peel, trying as best you can to retain as much of the interior flesh as possible. Use a smaller knife to trim away any recessed or hairy parts of the root.
Chop the celery root into roughly ½-inch cubes. (You should have about 8 ounces or about 2 cups.) Transfer to the bowl with the dressing, toss to combine, and season with salt and pepper.
Finely slice 1 bunch chives and add to the bowl. Stir to combine and chill until serving.
Dredge, fry, and serve the fish: Place ¼ cup flour in a shallow bowl or pie plate. Into a second dish, crack 1 egg and whisk until smooth. Place 1 cup panko in a third dish. Season all three dishes with salt and pepper and mix with a fork to combine.
Generously season two 6-ounce filets of cod with salt and pepper. Transfer to the dish with the flour and turn to coat. Transfer to the egg and turn until coated on all sides. Finally, dredge in the panko, gently pressing to ensure all sides are fully coated in panko.
To a skillet just large enough to fit the two filets of fish, add enough vegetable oil to reach about ½-inch up the sides of the skillet. Heat over medium-high for 2 minutes. Add a sprinkle of panko; if it sizzles, the oil is ready.
Add the filets to the skillet and cook until the undersides are golden brown, 3-4 minutes. Gently flip and cook 3-4 minutes, until the underside is golden brown.
Remove to a paper towel-lined plate to briefly blot any remnants of oil. Sprinkle with flaky salt and a drizzle of additional yuzu juice. Serve immediately, with the celery root remoulade alongside.
