Beef Tenderloin with Garlic Horseradish Cream

Put oven rack in middle position and preheat oven to 400 °F. Cut off and discard top fourth of garlic head. Drizzle exposed garlic with oil and sprinkle with 1/4 teaspoon salt, then wrap head tightly in foil. Roast garlic until tender, about 1 1/4 hours, then open foil and cool. While garlic roasts, simmer cream in a 1 1/2- to 2-quart heavy saucepan, stirring occasionally, until reduced to about 3/4 cup, 20 to 25 minutes, then transfer to a bowl. Squeeze garlic into a small bowl, discarding skins, and mash together with horseradish, pepper, and remaining 1/2 teaspoon salt using a fork. Stir garlic mixture into cream, then chill until ready to use.