Cut the bacon into strips. Heat 1 tablespoon of oil in a roasting pan over medium-high heat. Fry the bacon until crispy, about 5 min. Remove and set aside.
In the same pan with the bacon fat, fry the beef cubes in batches over medium-high heat until browned on all sides, about 3-4 min per batch. Season with salt and pepper. Remove and set aside.
Peel the carrot, 2 of the small onions, and the garlic cloves. Finely dice them all. Sauté in the pan fat over medium heat for 3-4 min until softened.
Return the beef and bacon to the pan. Sprinkle the flour over everything and stir for 1 min. Stir in the tomato paste and cook for 1 min.
Pour in the broth and red wine, stirring well. Bring to a boil. Season with salt and pepper, add the bay leaves and thyme.
Preheat the oven to 200 °C (392 °F) for electric, 180 °C (356 °F) for convection, or gas mark 3 (160 °C / 325 °F). Cover the roasting pan and braise in the oven for about 2 hours until the beef is very tender.
Clean and wash the mushrooms. Peel the remaining small onions. About 30 min before the beef is done, heat 1 tablespoon of oil in a separate pan over medium-high heat. Fry the mushrooms and onions until golden, about 5-7 min. Season with salt and pepper.
Add the mushroom and onion mixture to the casserole and return to the oven for the final 30 min. Wash and finely chop the parsley. Taste the casserole, season as needed, and sprinkle with parsley. Serve with baguette or gnocchi.