Mix flour, starch, baking powder, icing sugar and vanillin sugar. Add oil, eggs and egg liqueur and mix well with the whisk of the hand mixer. Grease a ring cake tin (21 cm Ø; 2.0 litres capacity) and sprinkle with breadcrumbs. Pour in the dough and bake in the preheated oven (electric: 175 °C/ gas: level 2) for 50-60 minutes. Leave the cake to rest in the pan for 10 minutes and then turn out onto a grid. Let it cool down. Dust with icing sugar before serving