Peel and roughly chop the potatoes, put them into a pan of salted water and bring to the boil. Cook until tender and then mash into a bowl.
Put the fish, with the smoked fish underneath, into a large skillet with the milk, parsley stalks and a good grinding of pepper. Bring the pan to a simmer and cook for about 5–8 minutes, turning if necessary.
Take the cooked fish out of the pan, flake it into a bowl and add the chopped parsley. Finely chop the hard-boiled eggs and add them with the mustard, lemon zest and juice.
Turn the flaked fish mixture into the mashed potato and mix very thoroughly. If you’re making these ahead, wait till contents of both bowls are cold before combining. Check the seasoning, adding salt and pepper as needed.
Crush the Ritz crackers which is very satisfying: put them in a freezer bag, bashing and rolling them with a rolling pin until they are crumbs. Line the bottom of a tray or shallow roasting pan with these crumbs.
Shape the fish and potato mixture into 10 fishcakes, each weighing approximately 10oz (4 inches across by an inch thick). As you make each fat patty, press them into the Ritz cracker crumbs on both sides to get a good coating and leave them in the tray or pan. I think they’re better not refrigerated but if you are making them a lot in advance, it would, of course, be better to sit them in the fridge.
When you are ready to cook them, preheat the oven to 400°F. Put the fishcakes on to a baking sheet, shaking off the excess Ritz crumbs but leaving a visible coating around each fishcake. Cook them for about 20 minutes or until they are heated through. If they are in the oven for too much longer they will crack a little, but no other harm comes to them, so don’t worry too much if people take a long time to make it to the table to eat.
Makes 10 fishcakes: these are so large no one is likely to need seconds, but it’s good to know you can provide more if required.