Add the beef stew meat, sliced mushrooms, pearl onions, minced garlic, beef broth, Worcestershire sauce, thyme, salt, and black pepper to the slow cooker. Stir to combine.
Cover and cook on low for 7 to 8 hours or until the beef is tender.
In a small bowl, whisk the heavy cream and cornstarch together until smooth. Stir the mixture into the stew.
Cover and cook on high for 20 more minutes until the broth thickens.
Ladle the stew into bowls and top with chopped fresh parsley before serving.