Cube the beef, pat dry and set aside. In a large cocotte, brown the lardons until lightly crisp. Remove the lardons. Add butter and oil to the rendered fat, then sear the beef in 2-3 batches.
When all the cubes are browned, return the lardons, the remaining meat and its juices to the cocotte. Add the onions and garlic. Sprinkle flour over the mixture, combine well and cook until the flour is golden brown, making sure to scrape the bottom of the cocotte.
Add the wine and enough water to barely cover the meat. Crush the bouillon cubes into the liquid, add the tomato paste, bouquet garni, 3 pinches of salt and some black pepper. Combine well. When the mixture comes to a boil, reduce the heat and cover the cocotte.
After about 2 hours of simmering, remove 150ml of the cooking liquid and let cool in the fridge. Clean the mushrooms and, if necessary, halve or quarter them. Peel the carrots and cut them in large chunks. When the liquid is cool, stir in cornflour and mix well.
Turn up the heat to medium. Add the prepared vegetables and cornflour slurry, stir well, and cook gently for about 30 minutes until the sauce is slightly thickened. Salt and pepper to taste. Remove the bouquet garni and sprinkle with plenty of chopped parsley before serving.