Bring a saucepan of salted water to the boil over medium heat. Add the barley and rice, and simmer for 30 minutes or until just tender. Drain well. Meanwhile, cook the broccolini in a pan of simmering salted water for 2 minutes, then drain and refresh in cold water. Set aside. Heat 1 tbs oil in a frypan over medium-high heat, add mushroom and cook, stirring occasionally, for 5 minutes or until golden. Add the prawns and cook for 2 minutes or until cooked through.