Peel, chop and boil the potatoes in boiling water until tender. Roughly mash with a fork.
Cook the fish in pan with a little oil until just cooked through. Once cooked, using your hands, separate the flakes.
Combine the potato, fish, onion, garlic, dill, lemon zest, 1 egg, mustard and season well. Form into 1/4 cup sized patties. Dust in flour, dip in egg and then into the panko crumbs.
Fry patties in olive oil until golden brown.
Notes
Makes about 8-10 depending on how big you make them.