In a medium sized saucepan cook the leeks in boiling salted water for 8 minutes. Drain, then place the leeks in a small bowl and season. Then drizzle with extra virgin olive oil and set aside.
In a small saucepan cook the potatoes in salted water until cooked, about 10 minutes.
In the meantime, mix together all the other ingredients except for the trout and rocket or watercress.
When the potatoes are cooked, drain them well then mix them into the crème fraise dressing. Then season.
Place two leeks onto each plate, then place a spoonful of the potatoes on the leeks. Arrange the smoked trout around the leeks and potatoes
Garnish with the rocket or watercress. Drizzle with extra virgin olive oil and serve.