-
1
Preheat oven to 475F.
-
2
Make seasoning mixture:
-
3
In a small bowl stir together seasoning mixture ingredients.
-
4
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.
-
5
Reserve
-
6
1 tablespoon seasoning mixture and rub remainder on top and sides of beef.
-
7
Roast beef in lower third of oven 20 minutes.
-
8
Peel potatoes and halve crosswise.
-
9
Remove pan from oven and skim all but about 1/2 cup fat from pan with a bulb baster or spoon.
-
10
Arrange potatoes around beef and turn with tongs to coat with fat.
-
11
Season potatoes with salt and pepper.
-
12
Reduce heat to 350F.
-
13
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 130F.
-
14
for medium-rare.
-
15
While beef and potatoes are roasting, separate mushroom stems and caps.
-
16
Slice caps 1/3-inch thick.
-
17
In a food processor pulse stems until chopped coarse and in a small saucepan combine with broth and water.
-
18
Simmer mixture 10 minutes.
-
19
Pour mixture through a sieve into a bowl, pressing hard on solids, and discard solids.
-
20
Transfer beef to a platter and let rest, covered loosely with foil, 20 to 30 minutes.
-
21
Transfer potatoes to another platter and keep warm.
-
22
With bulb baster or spoon skim all but about 1/4 cup fat from pan.
-
23
In pan on top of stove saute mushroom caps over moderately high heat, stirring, 2 minutes.
-
24
Add reserved tablespoon seasoning mixture, mushroom liquid, and any juices from beef and boil 5 minutes.
-
25
Stir in beurre manie and boil, stirring, about 3 minutes, or until thickened slightly.
-
26
Serve beef with sauce and sprinkle potatoes with parsley.
