Ingredients:

  • 2 tablespoons unsalted butter (30 ml)
  • 1 medium yellow onion, chopped (US: about 1 cup; metric: 150g)
  • 2 carrots, chopped (US: about 1 cup; metric: 120g)
  • 2 celery stalks, chopped (US: about 1 cup; metric: 120g)
  • 2 cloves garlic, minced (about 2 teaspoons)
  • 2 cups beef broth, low sodium (475 ml)
  • 1 cup pan drippings from roast beef (235 ml)
  • 1 tablespoon Worcestershire sauce (15 ml)
  • 1 teaspoon tomato paste (5 ml)
  • 1 sprig fresh thyme
  • 1 bay leaf
  • 1/2 teaspoon black peppercorns
  • 1 tablespoon cornstarch (or all-purpose flour) (15 ml)
  • 2 tablespoons cold water (30 ml)
  • Salt and freshly ground black pepper, to taste

Instructions:

  1. Melt butter in a large skillet over medium heat. Add onion, carrots, and celery and sauté until softened, about 5-7 minutes. Add garlic and cook for 1 minute more, until fragrant.
  2. If the pan where you roasted the beef has stuck bits, deglaze with the beef broth, scraping the bottom. Add this to the skillet in the next step, replacing two cups of beef broth.
  3. Add beef broth, pan drippings, Worcestershire sauce, and tomato paste to the skillet. Stir to combine.
  4. Add thyme sprig, bay leaf, and peppercorns. Bring to a simmer, then reduce heat to low and simmer for at least 30 minutes, or up to 1 hour, to allow flavors to meld.
  5. If desired, strain the au jus through a fine-mesh sieve to remove solids. Discard the solids.
  6. If you prefer a thicker au jus, whisk together cornstarch and cold water to form a slurry. Slowly whisk the slurry into the simmering au jus until it reaches your desired consistency. Simmer for 1-2 minutes more.
  7. Season with salt and pepper to taste. Serve warm with roast beef, prime rib, or French dip sandwiches.