-
1
Let the beef roast stand at room temperature for about 1 hour.
-
2
In a nonreactive bowl, combine the heavy cream and sour cream and whisk until smooth.
-
3
Add the lemon juice, salt, pepper and horseradish and whisk until blended.
-
4
Cover and refrigerate until ready to serve.
-
5
Position a rack in the bottom of an oven and preheat to 350u00b0F.
-
6
In a small saute pan over medium heat, warm 2 Tbs of the olive oil.
-
7
Add the garlic and fry, stirring constantly, until golden, 1 to 2 minutes.
-
8
Remove the pan from the heat and immediately skim the garlic from the oil, reserving the garlic.
-
9
Season the beef generously with salt and pepper and rub the fried garlic over the roast.
-
10
Set the beef on a rack in a roasting pan and roast until an instant-read thermometer inserted into the center of the meat registers 125u00b0F for very rare to rare, 1 3/4 to 2 hours; or 130u00b0F to 135u00b0F for medium-rare to medium, 2 1/4 to 2 3/4 hours.
-
11
Transfer the roast to a carving board, tent loosely with aluminum foil and let rest for 20 minutes before carving.
-
12
(The roast will continue to cook as it rests, so you can remove it from the oven 3 to 4 degrees below the desired temperature). Meanwhile, in a medium saucepan over medium-high heat, warm the remaining 2 Tbs oil.
-
13
Add the carrots, celery and leek, and saute until tender and golden, 6 to 8 minutes.
-
14
Add 4 cups of the stock and the thyme sprigs, bring to a simmer and reduce the heat to low.
-
15
Simmer until the liquid is reduced by half, about 1 hour.
-
16
After removing the roast from the pan, set the pan over medium heat, pour in the remaining 1 cup stock and whisk to scrape up any browned bits.
-
17
Pour the pan juices into the simmering broth, add the chopped thyme and simmer for 10 minutes.
-
18
Strain the sauce through a fine-mesh sieve set over a bowl.
-
19
Skim the fat, adjust the seasonings with salt and pepper, and transfer to a sauceboat or pitcher.
-
20
Carve the beef into 1/2-inch-thick slices and pass the sauce and the horseradish cream alongside.