Beef broth and consomme are both made from the water left behind after boiling beef, but consomme is clarified, usually by adding egg white. Consomme is typically concentrated by simmering to intensify the flavor. Broth can be served as it is, or used as a base for other soups.
The word “consomme” literally means "completed," referring to the process of clarification. The dish is believed to have originated in aristocratic kitchens of the Middle Ages as a lighter alternative to the heavy soups and stews eaten by the peasantry. Consomme remained a preserve of the wealthy for some time due to the quantity of meat required and the lengthy cooking process.
The popularity of consomme peaked during the Gilded Age of the late 19th century as a newly expanded upper class increased the demand for the elegant dishes of European fine dining. The great chefs of the age invented a dizzying array of consomme recipes.
To make a simple consomme, take some broth or stock and add beaten egg white. Simmer gently until the egg white begins to coagulate. When all the egg white has coagulated, carefully skim it from the liquid with a ladle or filter through a muslin cloth. If desired, remove fat by chilling the liquid and skimming the fat from the surface. Add herbs and seasoning to taste.