Wash the leeks and cut off both ends. Cut lengthwise, then into strips. Steam the leeks for 5 minutes. After cooking, rinse with cold water to stop cooking.
Cut endive lengthwise into strips.
In an ovenproof dish, add the cooked leek strips and the raw endive strips. Add the olive oil and vanilla, mix well and bake for 20 minutes at 180 °C.
Place the cooked vegetables on a plate and top with the trout fillet. Serve immediately.