1. Boil the potatoes in salted water until tender, about 20 minutes. Drain and dry off over the heat, mash and add the butter.
2. Flake the fish and add to the potatoes with the parsley and lemon juice. Taste mixture and season well with salt and freshly ground black pepper.
3. Shape the mixture into 8 flattish cakes by patting gently with your hands. The fish cakes can now be placed on a large plate, covered and refrigerated until ready to crumb and cook or left overnight if you want to make a day ahead.
4. Put the breadcrumbs, flour and beaten egg into separate flat dishes.
5. Coat the fish cakes in the flour first, then cover with egg, then breadcrumbs.
6. One-third fill a deep large frying pan with oil and over a medium heat, heat the oil until it starts to sizzle when you drop some crumbs into it.
7. Shallow-fry the fish cakes (in 2 batches) turning once to brown on both sides. Place on paper towel to drain off excess oil. 

Make a change

• Leave out the butter and add 2 Tbsp thick mayonnaise to the mashed potato.
• Try using panko crumbs, available in the Japanese or International section of your supermarket.
• 2-3 dill pickles or gherkins, drained and chopped, and/or 2 Tbsp drained and chopped capers are a nice addition to the mixture.