Pour 750 ml water, vinegar and salt in a small saucepan. After boiling the water, knocking the eggs one by one into a cup and placed low in the boiling water. Cook over low heat about 5 minutes Remove with a slotted spoon. Prepare sauce by making a light roux from the butter and flour, dilute with milk, add salt and boil until a thick sauce. Spread with butter a small pan, pour a little sauce, arrange on top eggs, add salt and pour the rest of the sauce. Sprinkle top with bread crumbs mixed with feta cheese, sprinkle a little butter. Bake until the feta cheese turn pink. Serve with salad and toast.