Preheat your oven to 325°F (165°C).
Heat olive oil in a large Dutch oven over medium-high heat. Brown the beef on all sides, about 4-5 minutes per side. Remove the beef and set aside.
In the same pot, add the chopped onion and carrots, cooking for about 5 minutes until softened. Add garlic and cook for another 1 minute.
Stir in the tomato paste and cook for 2 minutes. Add the beef broth, bay leaf, thyme, salt, and pepper. Stir to combine.
Return the beef to the pot, making sure it’s submerged in the broth. Cover the pot and transfer it to the oven.
Cook for 2.5 to 3 hours, or until the beef is fork-tender and falls apart easily.
If using, add potatoes and mushrooms in the last 30 minutes of cooking.
Remove the pot from the oven and discard the bay leaf.
Slice the beef and serve with the vegetables and broth. Garnish with fresh parsley. Enjoy your delicious Braised Beef!