The day before serving, remove the roast from the package, and dry thoroughly with paper towels.
Set the roast on a baking sheet, and place in refrigerator overnight.
Remove from refrigerator 1 hour before cooking time to allow meat to reach room temperature.
Rub the roast all over with horseradish and Dijon mustard.
In a bowl, mix together the kosher salt, black pepper, thyme, and garlic powder; sprinkle the spice mix over the roast.
Step 2
Preheat oven to 450 degrees F (230 degrees C).
Place the celery, carrot, and onion pieces into the bottom of a roasting pan.
Place the roast on top of the vegetables.
Step 3
Roast in the preheated oven for 30 minutes.
Reduce oven temperature to 350 degrees F (175 degrees C), and roast until the meat is browned and an instant-read meat thermometer inserted into the thickest part of the roast reads 130 to 135 degrees F (54 to 57 degrees C) for medium-rare.
Remove from oven, transfer roast to a platter, and cover with a tent of aluminum foil.
Allow to rest for 30 minutes.
Temperature of the meat will rise about 10 degrees during resting time.
Step 4
To make au jus sauce, skim excess fat from the pan drippings in the roasting pan.
Place the pan over a burner set to medium heat, and stir in the beef base and 1 1/2 cup of water.
Bring to a boil, scraping and dissolving any brown flavor bits from the bottom of the pan.
Strain out and discard the vegetables.
Combine the cornstarch and 1 teaspoon of water in a small bowl, and whisk the mixture into the sauce.
Allow the sauce to thicken slightly (sauce will be thin), pour into a gravy boat, and serve with roast.
Notes / Tips / Wine Advice:
Cook's Note I purchased a 6 1/2-pound roast, and this fed 4 adults and 2teens, plus I have leftovers