In a bowl whisk 3 cups of water plus 2 tablespoons of kosher salt until the salt is dissolved. Place the cod fillets into the salty water for 15-20 minutes. Remove the pieces from the salty water, reserving 1-2 teaspoons, and pat dry. Season with old bay, garlic powder, and dried dill.
In a separate container, blend the flour, salt, garlic powder, and paprika. Create a coarse crumble by pouring the reserved brine water into the flour and pinching it between your fingers.
Batter the fish in the crumbly flour the allow the fillets to rest in a baking sheet. Heat about 2 cuts is cooking oil in a skillet to 350 degrees. Fry the pieces for 3-4 minutes per side or until crisp. Drain on a wire rack before building the sandwiches as desired.
To make the sauce, blend all of the ingredients until smooth. Refrigerate until ready for use.