Boil the potatoes with all the peel, cutting them into 4 parts. Once softened, mash with a potato masher, getting a smooth and creamy texture. Combine eggs, salt, butter, and mix with your hands until the mixture is smooth and homogeneous. Grease a pan and sprinkle it with breadcrumbs. Lay down half of the potato mixture creating a kind of shell, and insert the anchovies in the center, cover with the remaining potato mixture and add a sprinkling of breadcrumbs. In the oven, bake at 200 degrees, for 8 minutes.