Cut the white leek and the shallot into fine pieces.
Melt some butter in a pan and add leek and shallot. Mix, cover and cook for +/- 20 minutes. If there is too much water in the preparation, let it evaporate over high heat.
Place the foie gras and the cream in a small saucepan. Heat over medium heat until the sauce is smooth (do not bring to a boil) and season to taste. When the cream is warm, whisk some air into getting to obtain a nice foam.
Heat the ravioli in lightly salted boiling water for 5 minutes and drain well.
Arrange the ravioli alternately with some leek fondue and finish the dressing with the foie gras foam.