Christmas Roast - Huckleberry's Natural Market

Ingredients

• 1 (6 pound) roast
• 2 tablespoons prepared horseradish
• 2 tablespoons Dijon mustard
• 2 teaspoons kosher salt
• 2 teaspoons coarsely ground black pepper
• 2 teaspoons dried thyme
• 2 teaspoons garlic powder
• 2 stalks celery, cut into 2-inch pieces
• 1 carrot, cut into 2-inch pieces
• 1 small unpeeled onion, quartered and separated
• 2 teaspoons concentrated beef base (paste)
• 1 ½ cups water
• 1 teaspoon cornstarch
• 1 teaspoon water