Line a box mould (approx. 10 x 25 cm; approx. 1 1/2 l capacity) with cling film. Sift icing sugar and cocoa. Melt the white fat and let it cool down lukewarm
Beat the eggs, icing sugar, cocoa and vanillin sugar with a hand mixer for 2-4 minutes until creamy. Gradually add the fat in a thin stream while stirring constantly, then stir in the liqueur
Place 1 layer of biscuits on the bottom of the box mould, cutting some in half. Spread 1/4 chocolate cream on top. Place alternately 1 layer of biscuits on top and spread 1/4 chocolate cream on top, finishing with the chocolate cream. Cover and leave to cool for at least 5 hours, preferably overnight.
Turn the cake out of the tin, remove the foil. Decorate with orange, mint and possibly 1 biscuit. Keeps in a cool place for up to 7 days. Tastes good with ice cream