Preheat the oven to 375 degrees F (190 degrees C).

Scrub the potatoes clean. Transfer the potatoes to a saucepan and cover with cold water: Cover the potatoes with an inch or two of cold water. Starting the potatoes in cold water helps them cook more evenly. Set the pan over medium-high heat and bring the water to a boil. Once boiling, reduce the heat to a bare simmer to cook the potatoes. Do not cover. Potatoes are done when tender, after about 20 minutes. When the potatoes are cooked clean it from the shell while still hot and run them under cold water to cool them down. Cut the potatoes into slices.

Hard boil 4 eggs, clean them from a shell and also cut them into thin slices.

Cut the sausages into thin slices.

At the bottom of the baking dish put the oil, chopped onion and start layering: 1 layer of potatoes, 1 layer of eggs and 1 layer of sausages, and each layer of potatoes season with a little salt and pepper. Layer ingredients until they are used up, finished with potatoes.

Beat the egg and mix in sour cream.

Pour egg and cream mixture over potatoes and put the dish in the oven, and bake until golden brown around 20-30 minutes.