Heat olive oil in a large skillet over medium-high heat.
Add beef cubes in batches and brown on all sides, about 3-4 minutes per batch. Transfer browned beef to the crock pot.
In the same skillet, add diced onion and cook for 3-4 minutes until softened.
Add minced garlic and sliced mushrooms to the skillet and cook for another 4-5 minutes until mushrooms release their moisture and begin to brown.
Transfer the onion, garlic, and mushroom mixture to the crock pot with the beef.
Pour beef broth and Worcestershire sauce into the crock pot.
Add dried thyme, dried rosemary, black pepper, and salt. Stir gently to combine.
Cover and cook on low for 6 hours, or until beef is tender.
About 30 minutes before serving, mix cornstarch and cold water in a small bowl to create a slurry.
Stir the slurry into the crock pot to thicken the sauce.
Cover and cook on high for 30 minutes until the sauce has thickened.
Sprinkle chopped fresh parsley over the dish before serving.