Created by Derf on December 20, 2011
Step 1: Preheat oven to 325f degrees. With a sharp knife tip, cut about 40 slits all over roast. Stuff each slit with a garlic sliver.
Step 2: In a small bowl, whisk together mayonnaise, horseradish, sage, salt and pepper, brush all over roast. Place onions in centre of roasting pan, place roast on top of onions. Roast in 325°F oven until thermometer registers 160°F for medium, about 2 hours. Transfer to cutting board and tent with foil, let stand for 10 minutes before carving
Step 3: Skim fat from pan juices. Pour in beef stock and Worcestershire sauce, bring to boil, stirring scraping up brown bits. Whisk cornstarch with 1 tablespoon water, whisk into pan and cook, whisking until thickened and glossy, about 2 minutes. Strain and serve with beef.