Heat oil in a medium size skillet or pan. Sauté onion until lightly golden. Add leek and cook for 5 more minutes, stirring frequently.
Process leek and onion preparation until a thick cream is obtained. Transfer preparation to a bowl. Season. Stir in cheese. Add 2 egg whites slightly beaten. Whip remaining egg whites until firm and fold into preparation.
Brush little oil in ramekins and fill with leek preparation.
Bake in preheated oven, 350 °F (180 °C), over hot water, for 45 minutes or until set.Cool, unmold and serve with carrot sauce.
Prepare a thick, light béchamel sauce. Place 1 cup cold milk in a medium size pan. Add cornstarch and stir constantly until sauce thickens. Remove from heat and add butter.
Cook carrot in chicken bouillon and bring to a boil. Reduce liquid to half. Season.
Process cooked carrot with béchamel sauce and add a few drops of lemon juice. Season.
Pour over leek puddings.
Decorate with parsley leaves.