Try serving lentils under (or with) any meat dish. They're hearty and earthy much more elegant than mashed potatoes (and easier to prepare).

Bring broth to a boil. Add the butter and the rinsed lentils. Boil about until lentils are tender but still firm (about 20 minutes). In a mixing bowl, add the vinegar, salt and pepper to taste. Serve under your main dish.