Add bacon to a large Dutch oven or stock pot. Turn heat to medium-low and cook, turning flipping every so often, until browned. Remove to a paper towel lined plate and then chop into small pieces.

Pat beef cubes dry with paper towels and add to a ziplock bag with flour, salt and pepper. Toss well to coat.

Heat the pan with bacon grease over medium-high heat. Once hot, add the beef in 2-3 batches (so not to overcrowd the pan), adding a little oil as needed, searing for a few minutes on each side, until browned. Remove meat to a plate and set aside. Reduce heat to medium.

Add onion and cook for 2-3 minutes. Add garlic and cook for 30 seconds. Add vinegar and wine to the pan, cooking over medium-high heat, and scraping up any browned bits from the bottom of the pan. Simmer for 10 minutes.

Add beef broth, bullion, tomato paste, bay leaves, thyme and rosemary. Season with a little more salt and pepper. Add beef and bacon back to the pot. Bring to a boil then reduce heat to a simmer.

Cover and cook for 1 1/2 hours or until beef is tender.

Meanwhile, chop the potatoes, carrots, and slice the mushrooms. Set aside.

Cook mushrooms (if using): Add 2 tablespoons butter and 1 tablespoon olive oil to a saute pan over medium high heat. Add mushrooms to the pan in a single layer. Cook for several minutes (without touching). Once golden on the bottom, flip to the other side and cook for a few more minutes.

Add mushrooms, potatoes, carrots and frozen pearl onions to the soup pot and cook for 15-20 more minutes, until carrot and potatoes are tender.

Taste broth. Season as needed with additional salt, pepper, bullion, rosemary, thyme, or some garlic powder. Add a sprinkle of crushed red pepper, if desired.

Ladle some of the hot broth into a bowl and whisk the flour into it, until smooth. Add to pot and cook for 2-5 minutes, until broth has slightly thickened.

Garnish with fresh parsley. Serve with artisan bread.