Best Prime Rib in Garlic Butter

Bahan-bahan (8 porsi)

• 6.6 pounds standing rib roast (4 bone rib roast)
• 2 heads garlic (unpeeled and halved horizontally, unpeeled keeps it together)
• 1/2 cup unsalted butter
• 5 cloves garlic (minced)
• 1 tablespoon coarse salt
• 1 teaspoon black pepper
• 3 cups low sodium beef stock (or broth)
• 2 cups red wine
• 1 tablespoon cornstarch (cornflour - optional for a thicker sauce.)