Wash the Matjes filets under cold water then pad dry. Cut into small chunks and place into a mixing bowl.
Peel and core the apple and peel the onion. Half the onion and apple and then cut the halves into slices. Cut the gherkins into small pieces. Now add the slices onions, apples and gherkins to the mixing bowl. Add the capers, black pepper and salt. Pour the double cream and mix well. Leave to infuse overnight in the fridge.
Next day prepare the dish. Boil or steam the potatoes until tender.
Place the potatoes on a plate and add the infused fish mixture. Enjoy.