Heat a little oil in a large pan until hot to the point of smoking. Season the venison with salt and pepper and dust in the flour. Fry in hot oil to seal and colour.
Meanwhile, bring the stock to the boil in a separate pan and add the dried porcini mushrooms. Turn down to a simmer.When all the venison is sealed, remove it from the pan, add a little more oil and turn the heat down. Finely chop the onion and the garlic clove, add them to the pan, and cook for 3-4 minutes, but do not let them turn brown.
Slice the chestnut mushrooms and add them in. Cook until the onions turn soft, then add the venison chunks back inn. Add the tomato puree and cook for a further 3 minutes.
Add the red wine and allow to reduce by half. Add in any remaining flour, stirring continuously. Transfer the stock with porcini mushrooms into the pan with the meat. Stir well, season and add the thyme sprigs. Simmer on low heat for at least 90 minutes or until the meat is tender.
If the sauce is a little watery when the meat is cooked you can reduce it further. Remove the meat and keep in warm in a covered dish. Then bring the sauce to the boil and reduce it until it coats the back of a spoon. Cut any remaining butter into cubes and stir them into the sauce to give it a lovely shine.
Add the pre cooked pearl barley to the sauce and bring to a simmer. Once the sauce is hot, add the meat back in. Stir carefully and serve in a large cup topped with the golden bread croute.