While not entirely new, here is the potato dish we're serving with our whole roasted tenderloin.

Potato Gratin with Rosemary Crust

This gratin is awesome with prime rib or beef tenderloin. Rosemary is a bossy herb that can take over a dish, so use it sparingly. We call for only 1 Tbsp. to season the entire gratin.

• Yield: Makes 10 servings
• Total:2 Hours, 20 Minutes
Ingredients
• 1 (14.1-oz.) package refrigerated piecrusts
• 1 tablespoon chopped fresh rosemary
• 1/4 teaspoon freshly ground pepper
• 2 cups (8 oz.) shredded Gruyθre cheese, divided
• 1 1/2 pounds Yukon gold potatoes
• 1 1/2 pounds sweet potatoes
• 1 teaspoon kosher salt
• 2/3 cup heavy cream
• 1 garlic clove, minced
• Garnish: fresh rosemary sprigs
Preparation
1. Preheat oven to 450°. Unroll piecrusts on a lightly floured surface. Sprinkle rosemary, pepper, and 1/2 cup cheese over 1 piecrust; top with remaining piecrust. Roll into a 13-inch circle. Press on bottom and up sides of a 9-inch springform pan; fold edges under. Chill.
2. Meanwhile, peel and thinly slice Yukon gold and sweet potatoes.
3. Layer one-third each of Yukon gold potatoes, sweet potatoes, and salt in prepared crust. Sprinkle with 1/4 cup cheese. Repeat layers twice, pressing layers down slightly to fit.
4. Microwave cream and garlic in a 1-cup microwave-safe measuring cup at HIGH 45 seconds; pour over potato layers in pan. Sprinkle with remaining 3/4 cup cheese. Cover pan with heavy-duty aluminum foil. Place on a baking sheet.
5. Bake at 450° for 1 hour. Uncover and bake 25 minutes or until potatoes are done and crust is richly browned. Let stand 10 to 15 minutes. Carefully transfer to a serving plate, and remove sides of pan. If desired, carefully slide gratin off bottom of pan using a long knife or narrow spatula. Garnish, if desired.