Serves 4

Hazelnut oil adds a sweet nutty flavour and aroma to salad dressings and dipping sauces. It should be used sparingly so as not to overpower the other ingredients in a dish. Store it in a cool place away from strong light and odours.

4-6 medium fennel bulbs, trimmed and tough outer layers removed
1 tsp fennel seeds
Sea salt and freshly ground black pepper
25g butter
2 tbsp olive oil
1½ tsp caster sugar
1 tbsp sherry vinegar
4 sea trout fillets, with skin, 150g each

For the salad
125ml olive oil
1 tbsp hazelnut oil
2 tsp Dijon mustard
2 tbsp white wine vinegar
100g watercress
30g roasted hazelnuts, roughly chopped

1 Slice the fennel bulbs thinly. Crush the fennel seeds with a little salt using a pestle and mortar. Melt the butter with 1 tablespoon of olive oil in a saucepan and add the sliced fennel and crushed fennel seeds. Sprinkle over the sugar and some seasoning and cook over a high heat for 5 minutes, covered.

2 Uncover and continue to cook the fennel for 10 minutes over a high heat, stirring well until lightly golden. Add the sherry vinegar to deglaze and continue to cook for 5 minutes until the fennel is soft and caramelised. Check for seasoning.

3 Put the olive oil, hazelnut oil, mustard and vinegar in a small bowl and whisk together with some salt and pepper to make a dressing. Wash the watercress, dry well and remove any tough stems. Put the watercress in a mixing bowl and set aside.

4 Score the skin of the sea trout fillets at close intervals with a sharp knife. Heat 1 tablespoon of olive oil in a large sauté pan. Pat the fish dry with kitchen paper, then season on both sides with salt and pepper. Place the fish skin-side down in the pan and cook for 4-5 minutes until the skin is crispy and the fish almost cooked. Turn the fish over and finish cooking for about 30 seconds on the other side.

5 Spoon the fennel on to four warmed plates and sit the sea trout on top. Quickly toss the watercress in enough dressing to coat. Divide the watercress alongside the sea trout and scatter with the roasted chopped hazelnuts. Serve immediately.

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