Make the potatoes, peel and cut into slices, fry in butter with the diced onion and the pieces of ham.
Remove the bones from the herrings, gut them and cut them into pieces. Grease a gratin dish and put a layer of potatoes in the beginning, then add the pieces of roast and herring, diced onion and ham, and continue layering until everything is used up. The potatoes must be on top.
Mix the whipped cream with egg and flour, season with salt and pepper, then pour over the potatoes and put the remaining butter in flakes.
Bake in the oven at 150 degrees for about half an hour.
Tip: It’s best to use your favorite ham – then your dish will taste twice as good!