Peel the potatoes, rinse and cut into thin strips. Peel the onions, finely chop and saute in hot butter.
Rinse the anchovy fillets, pat dry and cut into pieces.
Grease a baking dish with butter. Alternately layer the potatoes, onions and anchovies in the baking dish. Season each layer with salt and pepper. Pour 200 grams (approximately 7 ounces) of cream on top. Bake for about 35 minutes at 175°C (approximately 350°F). Pour in the remaining cream, sprinkle with breadcrumbs and bake for another 15 minutes, until golden brown. Remove from the oven, let cool and serve.