Bring the Mirin and maple syrup to the boil simmer and reduce by half then remove from the heat, whisk in the miso and leave to cool. When its cooled sufficiently pour over your prepped salmon and leave to marinate overnight.
Peel and grate the beetroot and potatoes. Put them into a bowl. Boil a kettle of water and pour over the beetroot and potatoes, leave for a couple of minutes to soften the vegetables. Drain the water of and dry the mix well. Season with the salt and pepper and form into balls about the size of tennis balls, flatten them to a thickness of 1 centimeter.
Heat 2 large frying pans on a medium heat and split the oil between them, when the oil is hot add the rosti and cook for 2 minutes on each side, they should be crispy and golden.
Add the marinated fish to the other pan and cook skin side down for 4 minutes or until the skin goes crispy. Turn over and cook for a further minute. If the fillets are thick you may need to cook for a little longer.
Serve the fish on top of the rosti and spoon some of the cooking juices over the top.
«This marinade can be used on a variety of firm fish like cod or snapper.»