Clean, peel, wash and grate the celery and carrots into sticks. Clean lamb's lettuce, wash thoroughly and dab dry. Clean, wash and cut radicchio into fine strips. Quarter the apple, remove the core and dice the apple.
Finely dice the bacon. Coarsely chop the nuts. Leave bacon in a pan until crispy, deglaze with 1/2 cup of water and apple juice. Add lentils and simmer covered for 5 minutes. Add apple pieces and nuts, season with vinegar and continue to simmer for another 2 minutes.
Season to taste with sugar, salt and pepper. Arrange the salad on a plate and pour the vinaigrette over it.