Boeuf à la mode ("beef in the style") is a French version of what is known in the United States as pot roast. It is a way to prepare a tougher cut of beef (rich in connective tissue, and in older recipes often lardoned). The dish is prepared by first browning the beef in oil, lard, or bacon fat. Some recipes include a preliminary marinating step where the beef is marinated in a combination of wine and brandy before browning.
The browned beef is then braised in a liquid composed primarily of red wine with garlic and root vegetables (usually celery, carrots and onions) and herbs such as thyme, bay, or celery seed. Many recipes add tomatoes or canned tomato sauce, while others add beef broth and/or brandy or other distilled spirits. In some older recipes the addition of a calf's foot or soup bones would add gelatin to the braising liquid, which serves to thicken the resulting sauce.
To finish the dish, the braised beef is removed and set aside to rest. Meanwhile, the braising liquid is strained and reduced to a sauce. The beef is then sliced and served with the sauce made from the braising liquid.