Fried Fish Sandwiches and Tostones

Name: Fried Fish Sandwiches and Tostones
Ingredients: 6 catfish fillets, cut in half; 1 tablespoon iodized salt, plus more for seasoning; Juice of 3 limes; 2 teaspoons onion powder; 2 teaspoons garlic powder; 2 teaspoons smoked paprika; 2 teaspoons ground black pepper; 1 teaspoon ground white pepper, plus more for seasoning; 2 teaspoons dried parsley; 4 large eggs; 2 cups all-purpose flour; Vegetable oil, for frying; 2 tablespoons unsalted butter, softened; 12 brioche buns, split; 1 head lettuce romaine or iceberg lettuce, shredded; 1 large beefsteak tomato, sliced; ¼ cup mayonnaise; 8–10 Scotch bonnet peppers; 1 small Vidalia onion, roughly chopped; 1 teaspoon ground turmeric; 2 tablespoons yellow mustard; 1 tablespoon vegetable oil; ½ cup white vinegar; ½ cup water, or more as needed; 4 green plantains; Sea salt, for serving; Lime juice, for serving