Cook the potatoes whole, then peel them. Set aside.
Remove the skin of the salmon, then flake the flesh into a large mixing bowl. Add the potatoes, and using a fork, mash them into a textured mixture. Season with salt and pepper.
Roughly chop the spring onion and chilli (if used) and put them into a small food processor. Add the dill and whiz until you get rough paste. Add the egg and whiz for a few seconds.
Add the paste to the fish mixture and combine. Add enough flour to get a firm mixture, than can be shaped.
Heat some oil in a frying pan (or line a baking tray). Form patties from the mixture between your palms, then coat them in the remaining flour, shaking off any excess.
Fry the fishcakes on each side for 3-5 minutes until golden. Alternatively grill or bake them in a medium hot oven.
Serve with a crunchy salad.