Preheat the oven to 200'C.
Soften the butter to room temperature and then combine with the breadcrumbs, ground hazelnuts and orange juice. Add the salt and pepper and combine well.
Place this mixture between two sheets of baking parchment and spread to a thickness of 3mm, then chill in the fridge for 15 minutes.
Remove the skin and any pin bones from the cod steaks. Cut each steak into a rectangle 3cm wide and 9cm long.
Cut the chilled breadcrumb mixture into 6 rectangles a touch smaller than each of the cod steaks. Top each piece of fish with a rectangle of the breadcrumb mixture and place on a baking tray.
Wash and peel the parsnip and the sweet potatoes and then cut into 1cm dice.
Peel and finely dice the shallots.
Heat a frying pan and add a drizzle of olive oil. Add the shallots and a pinch of salt and cook until soft. Add the vegetables, butter and caster sugar and cook for minute or so. Add enough water to come 3/4 of the way up the height of the vegetables and leave to cook until all of the liquid has evaporated. Check that the vegetables are cooked and add more seasoning if necessary.
Transfer the fish to the oven and cook for 8 minutes.
Roughly chop the hazelnuts and then toast in a hot pan.
Peel and finely dice the red onion. Pick and chop the chervil.
Place the onions, hazelnuts, chervil, olive oil, balsamic vinegar and salt in a bowl and mix with a spoon.
Use a rectangular serving ring to plate the vegetables. Place the fish alongside and finish with sauce.
«If you prefer, you can toast the hazelnuts until golden brown in an oven heated to 180'C.»