Brown the Beef: In a sizable pot or Dutch oven, warm the olive oil over medium-high heat. Season the beef with salt and pepper, then add it in portions to prevent overcrowding. Brown each piece on all sides for approximately 5 to 7 minutes. Once the beef is nicely browned, take it out of the pot and set it aside for later use.

Sauté Vegetables: In the same pot, add the onions, garlic, carrots, celery, and mushrooms. Sauté for 5 to 7 minutes, stirring occasionally, until the vegetables start to become tender.

Add Tomato Paste and Deglaze: Stir in the tomato paste, cooking for 1 minute. Then pour in the red wine, scraping up any browned bits from the bottom of the pot. Let it simmer for 5 minutes to slightly reduce.

Combine Ingredients and Season: Return the seared beef to the pot. Incorporate the beef broth, Worcestershire sauce, thyme, rosemary, and bay leaves. Adjust the seasoning with extra salt and pepper to taste.

Slow Cook: Cover the pot with a lid and reduce the heat to low. Simmer gently for 2-3 hours, stirring occasionally, until the beef is tender and the flavors are well combined. (As another option, you can move the mixture to a slow cooker and let it cook on low for 6 to 8 hours.)

Optional Thickening: If a thicker stew is desired, whisk the flour with a few tablespoons of cold water to create a slurry. Stir it into the stew in the last 30 minutes of cooking and let it thicken.

Plate the Dish: Discard the bay leaves and taste for seasoning, adjusting as necessary. Top with freshly chopped parsley and serve warm.