Heat 2 tablespoons of olive oil in a large skillet over medium-high heat.
Season the beef cubes generously with salt and pepper. In batches, sear the beef on all sides until browned, about 5-7 minutes per batch. Transfer the browned beef to the slow cooker.
In the same skillet, add the remaining 2 tablespoons of olive oil. Sauté the onions and carrots until the onions are translucent, about 5 minutes. Add the minced garlic and cook for an additional minute.
Transfer the vegetable mixture to the slow cooker with the beef.
Add the beef broth, mushrooms, tomato paste, thyme, bay leaves, Worcestershire sauce, and adjust seasoning with salt and pepper to taste. Stir gently to combine.
Cover and cook on low for 7-8 hours or on high for 4-5 hours, until the beef is tender and the flavors are well blended.
Remove the bay leaves prior to serving.
Notes
Serve in shallow bowls, garnished with fresh parsley. Pair with crusty bread or creamy mashed potatoes.