How to Make It
Tie the parsley stems, leek green and bay leaf together with kitchen string. Place the herb bundle in a large saucepan and add the lentils, onion, celery, carrot and water and bring just to a boil. Reduce the heat and simmer, skimming frequently, until the lentils are just tender, about 30 minutes. Remove from the heat and let the lentils cool to room temperature.
Drain the lentils. Pick out and discard the herb bundle and vegetables. In a large bowl, toss the lentils with the chopped parsley, knockwurst, red onion and garlic. In a small bowl, whisk together the vinegar and mustard and season with salt and white pepper. Whisk in the olive oil until blended. Pour the dressing over the lentils and serve.