Prime Rib Roast with Portobello Mushrooms and Potatoes
Ingredients
For seasoning mixture:
- 1 tablespoon chopped fresh rosemary leaves
- 1 tablespoon chopped fresh thyme leaves
- 2 garlic cloves, chopped
- 1 1/2 teaspoons coarse salt
- 1 teaspoon freshly ground black pepper
- a 3-rib standing beef rib roast (about 8 pounds)
- 1 tablespoon vegetable oil
- 5 pounds russet (baking) potatoes (about 10)
- 1 1/2 pounds Portobello mushrooms, wiped clean
- 1 3/4 cups beef broth (or a 15 1/2-ounce can)
- 1 cup water
- a beurre manié made by kneading together 1 tablespoon softened unsalted butter and 1 tablespoon all-purpose flour
Garnish: chopped fresh flat-leafed parsley leaves (wash and dry before chopping)
Method of Preparation
Preheat oven to 475°F.
Make seasoning mixture:
In a small bowl stir together seasoning mixture ingredients. Put roast, ribs side down, in center of a flameproof roasting pan, 18 by 12 by 2 inches, and rub oil on top and sides of beef so herbs will adhere. Reserve 1 tablespoon seasoning mixture and rub remainder on top and sides of beef. Roast beef in lower third of oven 20 minutes.
Peel potatoes and halve crosswise. Remove pan from oven and skim all but about 1/2 cup fat from pan with a bulb baster or spoon. Arrange potatoes around beef and turn with tongs to coat with fat. Season potatoes with salt and pepper. Reduce heat to 350°F and roast beef and potatoes, turning potatoes occasionally to brown evenly, 1 1/2 hours, or until a meat thermometer inserted in fleshy part of beef registers 130°F for medium-rare.
