Heat 1 tablespoon of olive oil in a large casserole pot and pan fry the beef on all sides for about 2 - 3 minutes on each side. Peel the carrots and cut them on large chunks. Transfer the browned meat to a plate. Add another teaspoon of olive oil into a casserole pot. Add the carrots, onions (cut on quarters) and garlic. Fry for about 10 minutes on low heat.
Add the celery, parsley, thyme and leek. Increase the heat, add the red wine and bay leaf. Cook for about 5 minutes. Lower the heat, add the meat and 250ml of water. Cover with a lid and cook for about 3 - 4 hours on the lowest heat. Be careful the stew doesn't start to boil, it should slowly simmer.
Fifteen minutes before the end of the cooking time, prepare the dumplings. Rub the butter and flour together in a bowl until resembling fine breadcrumbs. Mix in brioche bread (cut on very small chunks), chopped parsley, baking soda and 3 - 4 tablespoons of water. Season with sea salt and ground black pepper. Bring the mixture together until you have a dough. Knead slightly, before forming into 8 small dumplings.
season to taste
When the stew is cooked, transfer the meat to a plate and shred it on small pieces, using forks. Transfer most of the cooked vegetables to a blender and blend into a puree. Transfer the puree and shredded beef back to the casserole, add the dijon mustard and season with sea salt and ground black pepper.
Arrange the dumplings around the edge of the casserole. Cook for another 20 minutes on low heat. Serve, bon appetite.