Preheat oven to 375°F (190°C). Slice beef alongside rib bones to open loin meat away from bones like a book.
Spread 4 tsp (20 mL) garlic paste and season with salt and pepper both inside the cut and on the roast. Tuck 8 thyme sprigs lengthwise inside cut.
Tie meat and bones together with butcher twine. Place meat, bone side down, on a wire rack set on a rimmed baking sheet. Roast for 1 hour on middle rack of oven, then reduce temperature to 350°F (180°C) and roast for another 1 hour and 20 min. or until a meat thermometer registers 160°F (71°C) when inserted into thickest part of roast, away from the bone.
Meanwhile, prepare shallot Worcestershire sauce. In a glass jar, combine Worcestershire sauce, shallots, remaining thyme, garlic seasoning paste and 1/2 cup (125 mL) of water and shake well. Set aside.
Remove roast from oven and rest, 20 min. Remove twine. Cut off rib bones and thinly slice meat. Serve with shallot Worcestershire sauce.
Substitute 1⁄4 cup (60 mL) Compliments Prepared Horseradish for 1⁄4 cup (60 mL) of the Worcestershire sauce and 2 tbsp (30 mL) chopped fresh chives for the thyme.