Preheat oven to 180 degrees C. Butter the bottom and sides of a 20x30cm baking dish.
Saute onions in the butter until translucent and soft.
Cook and drain lasagna as per packet directions.
Make potatoes as per packet directions for 12 servings. Combine the onions with the potatoes.
Place a layer of lasagna over the bottom of the baking dish. Cover with a layer of potatoes, sprinkle with cheese and pats of butter. Repeat ending with noodles sprinkling top with cheese and butter. Bake for 1 hour.