1.
Preheat the oven to 190°C (375°F, gas mark 5). Put the potatoes into a large pan and pour over boiling water to cover. Cook over a moderate heat for about 15 minutes or until tender.
2.
Meanwhile, lay 2 overlapping slices of Parma ham on a board and place a fish fillet on top, skinned side up. Combine the breadcrumbs with the hazelnuts, coriander, eggs and a little pepper. Spread one-quarter of this mixture on top of the fish, pressing it over evenly. Carefully roll up the fish and ham like a swiss roll. Repeat with the remaining Parma ham, sole fillets and hazelnut filling.
3.
Arrange the fish rolls in a lightly greased ovenproof dish. Pour over the wine. Using 15 g (½ oz) of the butter, put a dab on top of each roll. Cover tightly with foil and bake for 20–25 minutes or until the fish will flake easily.
4.
Meanwhile, drain and mash the potatoes, then beat in the milk, remaining 15 g (½ oz) butter and the rocket, and season to taste. Transfer to a serving dish and keep hot. Steam the asparagus for about 4 minutes or until just tender.
5.
Serve the fish, cut into slices, on individual warmed dinner plates, with the asparagus and potatoes.