Start by preparing the slaw. Toss the cabbage, carrots, salt, and a good amount of black pepper until fully coated. Let the cabbage mixture sit for 15 minutes to soften. In a small bowl, combine Dijon mustard, lemon juice, and sugar. Once the slaw mixture is slightly softer and more pliable, squeeze the veggies in your hands to remove excess moisture. Then, drizzle the dressing over the veggies and toss to coat
For the tartar sauce, combine mayonnaise, lemon juice, dill, pickles, and capers in a small bowl. Season with salt and pepper to taste
Next, prepare the fish. Preheat the oil to 350°F in a dutch oven or a heavy-bottomed pan. Mix 1 cup of the flour, corn starch, paprika, cayenne pepper, and baking powder in a bowl. Gradually stir in the beer until the mixture is smooth. Season with salt and pepper
Dredge each fish fillet in the remaining 1/2 cup flour, then dip into the batter, allowing the excess to drip off. Fry the fish in the preheated oil for about 4-5 minutes each until they're golden brown and cooked through
To assemble the sandwiches, spread the tartar sauce on both halves of each toasted bun. Place a fried fish fillet on the bottom half, top with a generous helping of the slaw, then cover with the top half of the bun
Serve the sandwiches with bread and butter pickles and lemon wedges on the side