Green lentils are great in shepherds pie/bolognese/chilli/moussaka to replace all or part of the mince. Also you can cook them v simply with tomato/onion/garlic etc for a plain accompaniment to meat.
If you cook your green lentils first (I use the tiny green ones from Sainsers, they take about 40 minutes), you then need to fry a sliced onion or two and some garlic, add a chopped carrot and a chopped celery stick, let it sweat for a while. Then add onions, glass of wine (red or white), tin of tomatoes or a few fresh chopped ones, stock/water and simmer until the veg is soft. Really nice with lamb chops or roast lamb or meatballs and pasta.