Guinness Beef Stew by Kara Lydon

– 2 tablespoons olive oil, divided
– 1.5 lbs lean beef stew meat (round chuck)
– 8 ounces sliced mushrooms (white button or crimini/baby bella)
– 1 can Guinness (14.9 ounces)
– 1 large yellow onion, diced
– 2 celery sticks, diced
– 2 cloves garlic, minced
– 2 tablespoons tomato paste
– 2 teaspoons Dijon mustard
– 1 tablespoon Worcestershire sauce
– 1 tablespoon sugar
– 2 bay leaves
– 2 sprigs fresh thyme
– 1 cup beef stock
– 1 1/2 lbs yukon gold potatoes (about 4), peeled and quartered
– 4 to 5 carrots, peeled and sliced
– 2 teaspoons cornstarch
– Salt and pepper to taste