New England Pot Roast

Name: New England Pot Roast
Ingredients: One 3-pound beef chuck roast; Kosher salt and freshly ground black pepper; 3 tablespoons extra-virgin olive oil; 3 stalks celery, cut into 2-inch chunks; 2 carrots, cut into 2-inch chunks; 2 medium onions, cut into 2-inch chunks; 1/4 cup all-purpose flour; 3 cloves garlic; 3 sprigs fresh thyme; 2 dried bay leaves; 1 sprig fresh rosemary; 1/2 cup dry red wine; 6 cups beef stock; 1 pound red potatoes, cut into 2-inch chunks; 1/4 cup yellow mustard; 2 tablespoons prepared horseradish, drained; Chopped fresh parsley, for garnish, optional