1litre hot, good quality vegetable stock(~ 4 cups)
Heat the oil in a large, deep frying pan, and add the onion and mushrooms. Cook for 5 minutes over a medium heat, until soft.
Add the pearl barley, water and stock, along with the dried thyme, bay leaf, and a generous amount of black pepper. Bring to a simmer, and cook for around 45 minutes, or until the pearl barley is completely cooked.