Ingredients

1. 5 flat-leaf parsley sprigs, stems reserved and leaves coarsely chopped
2. 1 leek, green part only
3. 1 bay leaf
4. 1 pound French green lentils (2 cups), rinsed and picked over
5. 1 large yellow onion, halved lengthwise
6. 1 celery rib, halved crosswise
7. 1 large carrot, halved crosswise
8. 2 quarts cold water
9. 1 pound cooked knockwurst, casing removed, sausage sliced 1/4 inch thick
10. 1 small red onion--thinly sliced crosswise, rinsed in cold water and patted dry
11. 1 garlic clove, minced
12. 2 tablespoons red wine vinegar
13. 1 1/2 tablespoons Dijon mustard
14. Salt and freshly ground white pepper
15. 3 tablespoons extra-virgin olive oil

Directions

1. 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.
2. 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.

Make Ahead

The cooked lentils can be refrigerated in their cooking liquid for up to 2 days. Bring to room temperature before proceeding.