Sear Beef Cubes:
Heat 1 tablespoon olive oil in a skillet over medium-high heat. Sear half the beef cubes until browned on all sides, then transfer to a plate. Add the remaining oil and brown the second batch. Place all beef and accumulated juices into the slow cooker.Sauté Onion and Garlic:
Sauté the onion in the same skillet for 3-4 minutes, then add garlic and cook for 30 seconds. Transfer this mixture to the slow cooker.Combine Remaining Ingredients:
Combine all remaining ingredients except bay leaves and cornstarch in the slow cooker. Mix thoroughly.Add Bay Leaves and Cook:
Carefully add bay leaves. Cook on low for 10 hours, until the beef is fork-tender.Thicken with Cornstarch:
For a thicker consistency, whisk cornstarch with 2 tablespoons cold water, stir into the stew, and continue cooking until thickened, about 10 minutes.