Season the beef cubes with salt and black pepper.

In a large pot or Dutch oven, heat olive oil over medium-high heat. Add the beef cubes and brown them on all sides. Work in batches to avoid overcrowding the pot. Remove the browned beef and set aside.

In the same pot, add chopped onions, carrots, and garlic. Sauté until the vegetables are softened.

Pour in the red wine, scraping the bottom of the pot to deglaze it. Add beef broth, tomato paste, dried thyme, and bay leaves. Stir well.

Return the browned beef to the pot. Bring the mixture to a simmer, then cover and cook over low heat for 2 to 3 hours or until the beef is tender.

In a separate pan, sauté mushrooms in butter until they release their juices and become golden brown.

Add the sautéed mushrooms to the beef stew.

In a small bowl, mix flour with a bit of water to make a paste. Stir the flour paste into the stew to thicken the sauce.

Simmer for an additional 15-20 minutes until the sauce thickens.

Adjust seasoning with salt and pepper as needed. Remove bay leaves.

Serve the Beef Bourguignon over mashed potatoes, noodles, or crusty bread. Garnish with chopped fresh parsley.