Pre-heat oven to 180°C/350°F. Add butter, confectioner’s sugar, vanilla sugar, salt, and lemon zest to a large mixing bowl and beat for approx. 5 min. Add eggs and beat for approx. 1 min. more.
In a large bowl, mix flour and ground almonds and add to egg-butter mixture a little at a time, forming a fluffy dough. Add dough to a piping bag.
On a lined baking sheet, pipe dough into different shapes, leaving at least 1-cm/0.4-in. space between each cookie. Transfer to oven and bake at 180°C/350°F for approx. 12 min., or until golden brown. Remove from oven and leave to cool.
In the meantime, roughly chop chocolate, add to a small bowl, and place on top of a saucepan filled with simmering water to make a double boiler. Stir gently until melted. Coat one side of the cookies with the melted chocolate and leave to dry on a cake rack. Enjoy!