Preheat oven to 325°F. Pat beef cubes dry and season generously with salt and pepper. Toss with flour until evenly coated.

In a large Dutch oven, cook bacon over medium heat until crispy, about 5 minutes. Remove bacon and set aside, leaving fat in pot.

Working in batches to avoid overcrowding, brown beef cubes on all sides in the bacon fat, about 8-10 minutes total per batch. Transfer to a plate.

Add onion to the same pot and cook until softened, about 5 minutes. Add garlic and tomato paste, cooking for 1 minute until fragrant.

Pour in red wine, scraping up any browned bits from the bottom of the pot. Let simmer for 2 minutes to cook off some alcohol.

Return beef and bacon to pot. Add beef broth, thyme, and bay leaves. Liquid should almost cover the meat - add more broth if needed.

Bring to a gentle simmer, then cover and transfer to oven. Cook for 1.5 hours.

Add mushrooms to the pot, cover, and continue cooking for 30-45 minutes until beef is fork-tender and sauce has thickened.

Remove thyme sprigs and bay leaves. Taste and adjust seasoning. Garnish with fresh parsley before serving.