Place the roasting pan over medium-high heat on the stove. Use the residual fat and juices from the roast.
Add the sliced onions and minced garlic, cooking for about 5 minutes until soft and golden.
2 whole large onions, 5 cloves garlic
Sprinkle the soup mix over the onions and garlic and stir for 1 minute.
6 tbsp French onion soup mix
Add the beef consommé, beef broth, sherry (if using), Worcestershire sauce, soy sauce, and water to the pan.
1 can beef consomme, 1 cup beef broth or beef stock, 1/4 cup dry sherry or white wine, 2 tbsp Worcestershire sauce, 1 tbsp soy sauce, 1 cup water
Bring the mixture to a boil, then reduce heat to low and simmer for 45 minutes to develop the flavors, stirring occasionally. Add more water if necessary to maintain volume.
Strain the liquid through a fine mesh strainer into a bowl or pot, reserving both the liquid (for dipping) and the cooked onions.