Place the panko breadcrumbs into a bowl and set aside until needed.
Place the fish and potatoes into a large bowl and mash. Alternatively, if you would prefer your fish cakes to have a ‘smooth’ consistency, you can process these ingredients in a food processor.
Add the milk, parmesan cheese, garlic, lemon rind, onion flakes, mustard, egg and salt and pepper and stir well to combine.
Use a large dessert spoon to scoop up the mixture and shape with your hands to form a ball.
Place the ball into the panko breadcrumbs and gently roll to coat.
Place the coated fish cakes onto a plate and repeat steps 4 and 5 until all of the mixture has been used.
Transfer the fish cakes to the fridge for 30 minutes to chill, this will help them to hold their shape.
Heat 1 tablespoon of olive oil in a large frying pan over a medium heat and add 4 - 5 fish cakes. The amount of fish cakes you can cook at a time will depend on the size of your frying pan. Cook for 3 minutes before carefully flipping and cooking for a further 2 minutes on the other side or until nice and brown.
Repeat until all of your fish cakes have been cooked.