For the vinaigrette, whisk lemon juice, salt, pepper, stock and honey. Beat the oil into the vinaigrette drop by drop. Peel and finely dice the onion and stir into the vinaigrette.
Peel kohlrabi and avocado and cut into fine cubes. Mix vinaigrette, kohlrabi and avocado. Clean, wash and halve the peppers. Fill the bell peppers with salsa and arrange on a plate. Garnish with mint.