Preheat slow cooker to low setting OR preheat oven to 350 degrees F (175 degrees C).
Using a sharp knife, make 5 or 6 deep slits around the top and side of the roast. Push the whole cloves of garlic down into the slits. Place the meat in a slow cooker OR a 10x15 inch roasting pan and pour the coffee over the meat.
Cook in slow cooker on low setting for 6 to 8 hours OR bake at 350 degrees F (175 degrees C) for 2 to 3 hours.
When roast is done, remove from slow cooker OR oven, and pour the drippings into a small saucepan over medium low heat. In a separate small bowl, combine the cornstarch and water. Mix well and add slowly to the drippings, stirring constantly. Simmer until thickened.
