Step 1

Generously season the roast with kosher salt and place in the refrigerator, uncovered, for at least one hour (and up to overnight). This is a good time to let your butter soften as well.

Step 2

Set sous vide to 132-degrees (for medium rare).

Step 3

Place the roast in a large vacuum bag or two ziploc bags (doubled up), seal, and place in the water bath.

Step 4

Sous vide for 6 - 10 hours. (8 - 12 hours if the roast is frozen.)

Step 5

Remove the beef from the bag, reserving the cooking liquid, and pat dry.

Step 6

Preheat oven to 550 degrees.

Step 7

In a small bowl, combine butter with garlic powder, rosemary, thyme, pepper and herbs de provence. Coat the top and sides of the roast with the garlic herb butter and place in a roasting pan.

Step 8

Roast the prime rib for 8-10 minutes, until the crust is golden (keeping a close eye on it).

Step 9

Remove from the oven and let rest.

Step 10

While the roast rests, make the au jus. In a large skillet, bring the sous vide cooking liquid and broth to a boil, reduce the heat and simmer until reduced by half. Skim off any solids that rise to the top.

Step 11

Serve sliced prime rib with au jus and horseradish on the side.