Place lentils and bouquet garni in a medium saucepan with lid. Add enough water to cover by 1½ inches. Cover and bring to a boil. Remove lid; reduce heat to medium low and simmer for 20-25 minutes or until lentils are tender but not mushy. Skim away any froth. Carefully drain lentils. Remove and discard bouquet garni. Place lentils in a medium mixing bowl. Refrigerate to cool for about 10 minutes, then add carrots, celery, scallions, red onion and parsley. Mix gently to incorporate. Add vinegar, oil, salt and pepper. Stir until mixture is well coated with the dressing. Refrigerate salad until ready to serve. Can also be served at room temperature, if preferred.