¬†Clean leeks and trim off and discard green tops and¬†outer leaves. Cut the white portion of each leek into pieces¬†about 21/2 in. long.
¬†Bring a kettle of water to boiling. Blanch the leek pieces¬†about 2-3 min. Drain well.
¬†In a small skillet, heat oil over medium heat. Saute the¬†leeks until nicely browned, turning pieces over as they¬†cook, about 6-7 min. Remove leek pieces and place them¬†in a baking dish with lid.
In a small saucepan, heat the butter over medium-low¬†heat. Slowly add flour, stirring continuously with a wooden¬†spoon. Let cook 1-2 min., then stir in soup stock, salt, and¬†lemon juice. Pour the sauce over leeks in the baking dish.
Cover tightly and braise in oven for 15 min.
While leeks are cooking, bring the kettle of water to boil¬†again, and blanch olives for 2-3 min. Drain well.
When leeks are cooked, add olives, and continue to¬†cook, uncovered, for another 10 min.