Preheat the oven to 325. Heat the oil in a flameproof casserole. Add the onions and carrots and cook over low heat, stirring occasionally, for 5 minutes or until the onions are softened. Meanwhile, place the flour in a plastic bag and season with salt and pepper. Add the stewing steak to the bag, tie the top and shake well to coat. Do this in batches, if necessary.
Remove the vegetables from the casserole with the perforated spoon to reserve. Add the stewing steak to the casserole, in batches, and cook, stirring frequently until browned all over. Return all the meat and the onions and carrots to the casserole and sprinkle in any remaining seasoned flour. Pour in the stout and add the sugar, bay leaves, and thyme. Bring to a boil,cover and transfer to the preheated oven to bake for 1 3/4 hours.
To make the herb dumplings, sift the flour and salt into a bowl. Stir in the suet and parsley and add enough of the water to make a soft dough. Shape into small balls between the palms of your hands. Add to the casserole and return to the oven for 30 minutes. Remove and discard the bay leaves and serve, sprinkled with parsley.