In a large saucepan of boiling water, add the bouquet garni and barley. Cook the barley until tender, about 30 minutes. Remove bouquet garni and discard. Drain and set aside.
Heat a large skillet over medium heat. Pour the oil, add the onion, garlic, mushroom Italian seasoning or Herbes de Provence and cook over moderate heat while stirring for 5 minutes, or until the mushrooms have released some of their juices and the onions are translucent
Stir in the lemon juice and barley, season with salt and pepper and cook for 2 minutes.
Remove from the heat and transfer to a serving dish if preferred. Garnish with watercress.
Use portobello mushroom or a mixture of mushroom. Add meat, poultry or seafood if preferred.