If using fresh salmon, remove skin and any bones and cut into 2cm cubes. Drain canned salmon. Boil potatoes in boiling salted water until cooked, but not overcooked. Cool then slice about 1cm thick. Fry onion in butter or oil until soft but not brown, adding the bacon or prosciutto (if using) after the first minute or two.

Grease a casserole dish then layer up the ingredients, starting with potatoes and ending with potatoes topped with cheese. Season as you go, then drizzle over the cream. While the layers will vary according to the size of your dish I put half the potatoes, then half the salmon and dill, followed by a sprinkling of cheese and fried onion, then seasoning. Then all the spinach (chopped if leaves are large), the rest of the salmon, dill and onion, the remaining potatoes and cheese and lastly the cream.

Bake for 40 minutes at 180°C or until golden brown on top. Serve with a salad or green vegetable.