Place the roasting pan from the roast beef on the stovetop over medium heat. You want to use the original pan at first; that's how you capture all those browned bits.
Add in the Worcestershire sauce, red wine, and any reserved beef drippings. Whisk rapidly until the browned bits from the pan are scraped up. If desired, you can transfer the au jus to a skillet at this point.
1 tablespoon Worcestershire Sauce, drippings from roast beef, 1 cup Red Wine
Add in the beef broth, then bring the au jus to a simmer. It's done!
1 cup Beef Broth
Serve hot with roast beef or as a dipping sauce for French Dip sandwiches, and enjoy!
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Notes
For a thicker, silkier sauce, add in 2 Tablespoons of unsalted butter while the au jus is simmering.
You can make au jus with beef broth, but it will taste less intense. Adding sauteed shallot, garlic, and herbs will bring some of that flavor back, just make sure to strain the sauce once it's done cooking. You will also need to add butter to make up for the lack of fat from the drippings.
For a huge flavor boost, add dried porcini mushrooms! They're packed with rich, earthy umami flavor! You can add dried pieces or powder. If using pieces, strain them out before serving.
Don't separate out the fat from the drippings! You'll want to keep it in; it adds silkiness and richness to the sauce.