While the machine is running, slowly drizzle in a scant 1/2 cup (125ml) of the chickpea liquid and puree very well, until the hummus is as smooth as possible. If necessary, add more liquid, a tablespoon at a time, until the hummus is the consistency of sour cream. (I ended up adding 2/3 cup but yours may take more or less.) Taste and adjust, adding another teaspoon of lemon juice or salt, if desired.