1. Preheat the grill. Toast the nuts in a single layer, stirring frequently, until  the skin split. Then tip the nuts on to a clean dish towel and rub to remove the skins. Leave the nuts to cool, then chop them coarsely.

2. Heat 50g/2 oz of the butter in a large frying pan. Season the trout inside and out, then fry two at a time for 12-15 minutes, turning once, until the trout are brown and the flesh flakes easily when tested with a point of a sharp kitchen knife.

3. Drain the cooked trout on kitchen paper, then transfer to a warm serving plate and keep warm while frying the remaining trout in the same way. (If your frying pan is large enough, you could, of course, cook the trout in one batch).

4. Add the remaining butter to the frying pan and fry the hazelnuts until evenly browned. Stir the lemon juice into the pan and mix well, then quickly pour the buttery sauce over the trout and serve at once, garnished with slices of lemon and flat-leaf parsley sprigs.

Notes : You can use a microwave to prepare the nuts instead of the grill. Spread them out in a shallow microwave dish and leave uncovered. Cook on full power until the skins split, then remove the skins using a dish towel as described above.