Sift 250 g icing sugar. Beat the eggs and vanilla sugar with the whisk of the hand mixer, adding icing sugar by the spoonful until the mixture is thick and foamy. Slowly add the oil and egg liqueur and stir.
Mix flour, starch and baking powder, sieve over it and fold in until a smooth dough is formed. Grease a ring mould with a tube bottom insert (2 litres capacity) and dust with flour.
Pour in the dough and bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 1 1/2 hours. Let the finished cake rest in the pan for approx. 15 minutes, turn out onto a cake rack and let it cool down.
Dust with 1 tablespoon icing sugar.