Mushroom Stuffed Beef Tenderloin

5 tablespoons butter, divided1 pound assorted fresh mushrooms, large dice, such as porcini, white button and oysters1 shallot, finely diced1 1/2- to 2-pound beef tenderloinSalt and pepper to taste2 tablespoons olive oilSauce2 cups chicken stock1 cup heavy cream2 tablespoons butter2 tablespoons flourPotatoes2 pounds small, red potatoes3 tablespoons butterSalt and pepper to taste1 tablespoon garlic, chopped1 tablespoon chives, choppedRosemary sprigs, optional garnishIn medium frying pan melt 3 tablespoons of the butter and sauté the mushrooms and shallot until tender. Set aside to cool.Butterfly the tenderloin (or have your butcher do it). Press it flat. Season generously with salt and pepper.In a large frying pan heat the remaining 2 tablespoons butter and the olive oil and brown the meat on both sides. Remove to a clean work surface and place mushrooms on tenderloin. Roll up and secure the edges with toothpicks. Wrap in plastic and refrigerate at least 4 hours to overnight.For the sauce: Bring stock to a boil in medium saucepan and reduce by half. Add cream and let mixture simmer over low heat.In a separate small pan melt the butter and whisk in flour, cooking and stirring over medium-low heat for 1 to 2 minutes. Slowly add roux to cream mixture, stirring constantly until the sauce thickens. Keep warm.For the potatoes: Place potatoes in cold, salted water and bring to a boil. Cook until fork tender, about 20 to 25 minutes. Drain, cool and quarter the potatoes.In large frying pan melt the butter and brown the potatoes on all sides. Season with salt and pepper; add garlic and chives. Keep warm.Remove plastic wrap from meat and cut roll crosswise into 1 1/2-inch slices. Place slices in oiled baking dish and roast at 350 degrees for 20 minutes for medium rare. Remove and let meat rest 5 minutes.To plate: Mound potatoes in center of four serving plates. Top with a slice of tenderloin and spoon sauce over all. Garnish with rosemary sprig. Serves four.Cook's note: Serve with asparagus spears and Ravenswood Vintner's Blend Zinfandel.Nutrition values per serving: 865 calories, 69 g fat (35 g saturated), 33 g carbohydrates, 3 g fiber, 30 g protein, 199 mg cholesterol, 1,218 mg sodium.