Wipe the mushrooms with a damp cloth. Discard the shitake stalks and tear their heads into smallish pieces. Cut off the tougher stems of the oyster mushrooms and pull apart in a similar manner. Trim and thickly slice the chestnut mushrooms.
Heat the olive oil in a heavy bottomed saucepan and gently fry the garlic and onion until soft and golden. Add the mushrooms, adding a little more oil if needed, and continue to fry until they begin to soften.
Add the whit wine, stock and herb bundle and bring to a boil. Stir in the barley and season to taste. Leave to simmer for about 20 minutes or until the barley is tender.
When ready to serve remove the bunch of herbs and check the seasoning,then stir in the butter or cream and the freshly chopped herbs.