Yellow mustard seeds are one of the most popular and widely used varieties of mustard, and they are an important herb in many cultures worldwide. Despite a pungent bite, they are milder than their close relative, brown mustard, and are usually substituted when a less piquant flavor is wanted. Yellow mustard seed powder is often used to season regional culinary dishes such as hollandaise dressing, soups, sauces, marinades, and various spice rubs.