Pat beef dry with paper towels. In a bowl, combine flour with salt and pepper to taste. Add beef, a few pieces at a time, and toss until lightly coated.
Heat oil in a large skillet. Add beef in batches and cook until browned on all sides, about 20 minutes total. Place meat in a large slow cooker.
Add onions to skillet and cook until softened, about 5 minutes. Stir in garlic and tomato paste. Add wine and cook, scraping the pan, until liquid comes to a simmer. Pour contents of skillet over meat. Add broth, carrots, tomatoes and herbs to slow cooker. Cover and cook on LOW for 8 hours or until beef is tender when pierced with a fork.
When beef is almost ready, melt butter in a medium skillet over medium-high heat. Add mushrooms and salt and pepper to taste. Cook, stirring often, until mushrooms are golden, about 10 minutes.
Stir mushrooms into stew and discard bay leaf. Serve hot, sprinkled with parsley.