Finely chop the speculoos in a bag with a rolling pin or a blender. Mix the flour, sugar, vanilla sugar, baking powder and salt in a bowl. Add the oil, eggs and baking flavor and mix with a hand mixer.
Finally, mix in the speculoos crumbs and buttermilk. Raisins, cranberries, chopped nuts or chocolate sprinkles can be added as a filler.
Grease a loaf pan or bundt pan and sprinkle with breadcrumbs. Pour the dough into the mold and bake at 180 ° C (top / bottom heat) for 1 hour. Then turn off the oven and let the cake steep for another 10 minutes.
Take out and let cool for a few hours. If you want, you can refine the cake with powdered sugar or glaze.