Pre-cook and cook: 20 min.
Stir mustard, vinegar and oil well, season sauce.
Cut fennel cabbage into small pieces, set aside, shave fennel lengthwise into a large enough bowl. Place iceberg lettuce leaves as a bowl on plates, fill with fennel, drizzle sauce over.
Toast the bread cubes until golden brown, add the fennel fronds, mix, and spread the bread cubes evenly over the lettuce.