1. Preheat the oven to 400ºF (200ºC) and put 2 baking sheets in the oven to heat. Place the potatoes in a large saucepan and pour over enough boiling water to cover them. Bring back to a boil, then simmer for 5 minutes. Drain and return to the pan.
2. Drizzle the oil over the potatoes and toss them quickly to coat. Spread them out on one of the hot baking sheets and roast for 10 minutes. Turn the potatoes over and roast for another 10 minutes, then turn them again and roast for a further 5 minutes or until crisp and tender.
3. Meanwhile, tuck the sprigs of tarragon inside the trout with some pepper. Cut out 4 squares of foil, each large enough to wrap up a fish. Cut the orange and lemon slices in half. Divide half the orange and lemon slices among the foil squares, lay the trout on top and cover with the remaining fruit slices. Sprinkle 1 tablespoon orange juice over each fish. Wrap up the foil to enclose the fish completely, twisting the ends to seal. Place the parcels on the second hot baking sheet and bake for 20 minutes.
4. While the trout and potatoes are cooking, make the cucumber sauce. Grate the cucumber, place it in a sieve and press to squeeze out any liquid. Mix together the cucumber, yogurt and mint, and season with pepper.
5. Arrange the baked trout, orange and lemon slices and roasted potatoes on individual warm plates. Add a garnish of baby arugula and serve with the cucumber sauce.

PER SERVING

440 calories
48 g protein
13 g total fat
3 g saturated fat
115 mg cholesterol
32 g total carbohydrate
8 g sugars
6 g fibre
147 mg sodium

Like other oily fish, trout is rich in beneficial omega-3 fatty acids. It is also valuable for its high protein content and B vitamins, especially niacin and vitamin B12.