Mix the flour, poppy seeds, baking powder and salt. Using the mixer on medium speed, beat the margarine with sugar for 5 minutes until frothy. Then add egg substitute and vanilla sugar. On the lowest setting, add 1/3 of the flour mixture, then 1/3 of the cream or cream. Keep stirring until all the ingredients are mixed and a smooth dough is formed.
Bake for about 60 minutes. A knife must come out cleanly from the center after piercing.