Place all of the ingredients for the marinade in a bowl with the cubes of beef. Cover and refrigerate for about 12 hours, or overnight, stirring occasionally.
Strain the marinade into a saucepan, then remove the beef and set it aside, keeping the vegetables and bouquet garni separate. Bring the marinade to a boil, skim off the foam, and cook for 6 to 8 minutes. Strain through a fine sieve.
In a large, heavy-bottomed flameproof casserole or Dutch oven, heat a little oil and butter. Pat the meat dry and brown it on all sides in batches; remove and keep to one side. Add the well-drained vegetables from the marinade (don’t add the bouquet garni), lower the heat slightly, and cook, stirring occasionally, until they are lightly browned.
Heat the oven to 400°F. Return the meat to the pan, add the tomato paste, and stir over medium heat for 3 minutes. Sprinkle the meat with the flour and place it in the oven for 6 to 8 minutes; then carefully remove the hot pan and mix in the flour. Place the pot over medium heat again, add the marinade, and bring it to a boil, stirring constantly. Then add the beef stock and bouquet garni.
Lower the oven temperature to 325°F. Return the stew to a boil, cover, and transfer it to the oven. Cook for 1½ to 2 hours, or until the meat is very tender. Check occasionally to make sure the mixture isn’t boiling; you want to maintain just a very low, bubbling simmer.
Meanwhile, place the onions, some of the butter, sugar, and some salt in a deep skillet and pour in enough water to cover. Cook over medium heat until the water has almost evaporated, then swirl the skillet until the onions are golden. Fry the mushrooms in some sizzling butter until they turn golden; season and drain them and add to the onions. Fry the garlic and bacon in a little oil, drain, and add to the onions and mushrooms.
Melt a little more butter, brush the bread with it, and toast the slices in the oven for 3 to 5 minutes, or until brown.
Once the beef is fork-tender, skim off the excess fat. Transfer the beef to a clean, flameproof casserole or serving dish, cover, and keep warm. Strain the sauce and return it to the pan, discarding the vegetables and bouquet garni.
Bring the sauce to a boil and simmer for about 15 minutes, skimming frequently, until the sauce coats the back of a spoon. Season to taste with salt and pepper, strain it once more over the meat, and add the onions, mushrooms, and bacon. Simmer just until hot, about 5 minutes.
Dip a corner of each bread crouton into the sauce, then into the parsley. Sprinkle the remaining parsley over the stew, and serve with the croutons on the edge of the dish or on the side.