For the cornflakes, cream butter with sugar, salt, rum and vanilla sugar. Gradually add eggs. Stir in the chocolate. Finally, mix in flour and cornflakes.
Pour the mixture into a piping bag and pipe small biscuits onto a prepared baking tray using a smooth piping nozzle. Bake the cornflakes in the preheated oven at approx. 165°C to 175°C for 10 to 12 minutes until light brown on sight.