Whisk the mayonnaise, sugar, mustard, vinegar, salt and pepper in a large bowl.
Add in the slaw mixture and toss to coat then cover and set aside in the fridge.
Whisk the egg and milk together in a large dish and add in the cod fillets and allow to soak
Place the flour and seasoned salt in a bowl and mix to combine, add in the panko breadcrumbs and stir well.
Take a wide bottomed pan and pour in the vegetable oil to come up about one and a half inches. Heat over a medium to high heat.When a breadcrumb dropped into it sizzles it is ready to fry the fish.
Take the fillets of fish out of the egg and milk mixture and drop into the flour and breadcrumb mixture. Cover on all sides then drop into the hot oil.
Cook for between 2-4 minutes on each side until golden brown then remove and drain on kitchen paper.