Mix the margarine, egg, sugar, vanilla sugar and salt until frothy. Gradually stir in the flour and cornstarch. If necessary, add water and, when the batter is nice and creamy, stir in the chocolate.
Place small piles on a baking sheet. Bake the cookies in a preheated oven (approx. 190 ° C). The duration depends on the size of the cookies, when the cookies are lightly brown on the underside, the cookies are ready.