As soon as it evaporates add half of the cup of water (if you happen to be boiling pasta in the next pot, use that water), turn down the heat and simmer over low heat and with the lid on the frying pan until the broad beans get tender. Halfway into cooking (or even sooner) add the rest of the water (if necessary add a little more later). When the broad beans are ready they should have a little sauce. But just a little. (The process should take about 30-35 minutes, so, be sure to try them to see if they are ready).