If using a pressure cooker, bring up to pressure, lower the heat to a minimum and cook for 15 minutes, then release the pressure. When you open the cooker, check for liquid: if the barley has entirely absorbed it, add more water or broth and let things simmer for a few minutes more. If there is too much liquid (less likely, given barley's aborptive qualities) then just let is simmer until you have reached the proper consistency.