 Olive oil was a ubiquitous ingredient in Mediterranean cultures, but remained an expensive import in the north where oils of poppy, walnut, hazel and filbert were the most affordable alternatives.Butter and lard, especially after the terrible mortality during the Black Death made them less scarce, were used in considerable quantities in the northern and northwestern regions, especially in the Low Countries.Almost universal in middle and upper class cooking all over Europe was the almond, which was in the ubiquitous and highly versatile almond milk, which was used as a substitute in dishes that otherwise required eggs or milk, though the bitter variety of almonds came along much later.