Sous Vide Prime Rib

1 . Stage

Prepare a thermocirculator and water bath according to manufacturer's directions. Set thermocirculator to 135 degrees F (57 degrees C) and allow water bath to come up to temperature. Season rib roast evenly with 1 tablespoon salt and transfer to a large vacuum-sealable bag; arrange butter cubes, thyme sprigs, and crushed garlic around rib roast in bag.

2 . Stage

Seal bag with a vacuum sealer according to manufacturer's directions. Transfer vacuum-sealed rib roast to warm water bath with thermocirculator, cover vessel with aluminum foil to reduce evaporation, and cook for 6 hours. Remove rib roast from bag; roast will be at 135 degrees F (57 degrees C) when pulled from water bath. Transfer to a rimmed sheet pan lined with paper towels and gently pat dry; reserve contents remaining in bag.

3 . Stage

Preheat the oven to broil with an oven rack positioned about 10 inches below the heat source. Line a rimmed baking sheet with aluminum foil and fit with a wire rack.

4 . Stage

Season rib roast evenly with remaining tablespoon salt and pepper and place on the prepared baking pan.

5 . Stage

Cook rib roast in the preheated oven until fat cap is deeply caramelized, 8 to 10 minutes. Transfer rib roast to a large cutting board and let rest for 10 minutes before slicing against the grain into 1- to 1 1/2-inch thick slices; garnish sliced prime rib with flaky sea salt to taste.

6 . Stage

While rib roast is in the oven, combine reserved contents from vacuum bag and mushrooms in a medium saucepan and cook over medium-high heat, stirring occasionally, until mushrooms are mostly tender and liquid has reduced completely, 8 to 10 minutes. Add wine and continue cooking, stirring occasionally, until wine is almost completely reduced, about 5 minutes. Add beef broth and continue cooking, stirring occasionally, until sauce is thick enough to coat the back of a spoon, about 15 minutes; remove thyme sprigs and discard. Season mushroom sauce to taste with salt and serve alongside sliced prime rib.