Preheat oven to 400F.
Trim cod fillets into even square shapes, removing thin bits at the ends of the fillets.
Prepare baking sheet by lining with foil and placing a cooling rack on top to create a baking rack.
Crush pretzels in a plastic bag by gently rolling with a rolling pin. This can also be done in a food processor (but who wants to clean that?). Pour crumbs into a small bowl, plate or onto wax paper on the countertop.
Coat fish by covering one side with ½ tsp Dijon, then dipping that side into the pretzel crumbs. Cover the clean side of the fish with ½ tsp Dijon and flip over into the crumbs. Press firmly to create a thick crust. Transfer to the backing rack. Continue with remaining fish pieces.
Bake for 15-18 minutes until fish is cooked through and flaky. Serve with fries and your favourite dipping sauces.