1. Pour enough rapeseed oil into a large heavy-bottomed saucepan or Dutch oven until it reaches a depth of 2 inches. Heat over medium heat until a deep-fry thermometer inserted in the oil registers 190°C.
2. Sprinkle the cod liberally with salt and black pepper on all sides. Place the flour, eggs and crushed potato chips into three separate shallow baking dishes. In batches, dredge each of the cod pieces first in the flour, then in the beaten eggs and finally in the crushed potato chips.
3. Fry the cod in batches until golden brown and crispy, 3 to 5 minutes. Remove using a slotted spoon and place on a baking sheet lined with paper towels to absorb any excess oil. Sprinkle liberally with sea salt and black pepper.
4. To assemble, place the fried cod pieces onto a large platter. Top each with 1/2 teaspoon or so of tartar sauce and garnish with a sprinkle of chopped dill.
5. Serve with any additional tartare sauce, lemon wedges and malt vinegar on the side.