The only changes/additions I have made: 1/2 can of tomatoe paste and 1 extra boullion cube. I used the bacon grease and it adds a nice rich flavor. I have also added 1/4 c. cooked ground beef or 1/3 c. barley which I liked even better than the meat. I increased the water content and just cooked the barley with the lentils.
This is a very easy recipe to make and it tastes great. I get 3-4 nice portions for my lunches at a low cost