Blend four sole pieces and offcuts with 75ml cream into a fine paste and transfer to a piping bag.
Season four sole pieces and place them on sheets of cling film.
Layer each piece with the fish mousse, another sole piece, more mousse, and a final sole piece.
Wrap the fish stacks tightly in cling film and chill until cold.
Simmer half of the cauliflower florets in the remaining 200ml cream for 5 minutes until tender.
Purée the cooked cauliflower and cream in a food processor and season.
Boil the remaining florets in salted water for 3 minutes and drain.
Grate the raw cauliflower and boiled egg into a bowl and mix with chives.
Whisk the balsamic vinegar and olive oil together in a separate bowl.
Steam the sole parcels for 8 minutes and remove the cling film.
Dress the cauliflower and egg salad with two-thirds of the vinaigrette.
Toss the cooked florets and langoustines with the remaining dressing.
Plate the purée, top with a sole stack, and arrange the two cauliflower salads on the sides.