Bonus tip: use a potato masher to chop and stir ground beef as it fries because it's much easier than trying to break it up with the side of a spoon. I also mashed at the lentils a bit, which made them even less discernible in the dish.
However, I'm not trying to hide the beef-stretcher from my family. They all know that the local organic beef I buy is expensive (but not when you consider our health and the environment!).