Short Rib Shepherds Pie

Name: Short Rib Shepherd’s Pie
Ingredients: 4 beef short ribs, each 2 1/4 to 2 1/2 lb. (1 to 1.25 kg); Sea salt and freshly ground pepper; 2 Tbs. extra-virgin olive oil; 1 large yellow onion, chopped; 2 celery stalks, chopped; 6 garlic cloves, crushed; 1 carrot, chopped; 3 1/2 cups (28 fl. oz./875 ml) dry red wine such as Syrah; 3 bay leaves; 1 Tbs. fresh thyme leaves; 4 cups (32 fl. oz./1 l) beef stock, or as needed; 1 1/2 lb. (750 g) Yukon Gold potatoes, peeled and quartered; 1/4 cup (2 fl. oz./60 ml) milk; 4 Tbs. (1/2 stick) (2 oz./60 g) unsalted butter; 1 egg yolk, beaten