Cook and crush the potato and refrigerate till cool. ( I steam whole in the skins and peel after)
Cut the tuna into pieces and put into a food processor and blitz till it is well minced but not completely smooth.
Then in a bowl, add the parsley, tuna, shallot, garlic, lemon juice, egg, salt and pepper and crumbs to the potato and mix well.
Shape the mixture into cakes flattening to around 5-6 cm so they are not too thick to cook through.
The recipe can be made to here and chilled if you want to cook them later.
Put 2 cups of panko crumbs into a dish and coat the cakes with the crumbs. Pushing them onto the outside so they stick. I had no need to eggwash, the crumbs should stick with no problems but you can egg them first if you prefer
Heat a fry pan with 3 cm of oil. When it is hot add the fish cakes in batches frying till golden on both sides, drain on kitchen paper.
Serve them with caper mayonnaise
This recipe makes approximately 8 fish cakes or around 12-14 small ones