FOR THE Dough: In a small bowl, mix egg yolk, water and vanilla and set aside.
In a second bowl mix flour, sugar and salt. Knead the butter until it forms an even dough. Then add the egg mixture and knead well. Form the dough into a ball, wrap in cling film and put in the fridge for 30 minutes.
Roll out the dough on the floured worktop. Grease a tarte/quiche tin with butter and place the dough inside, preferably without pressing. The rim should be 1.5 - 2 cm (one finger width) high.
Place the mould including the dough in the freezer for 15 minutes.
In the meantime, preheat the oven to 190 degrees and bake the dough for 25-30 minutes (until golden brown). Let it cool down and prepare the filling in the meantime.
FOR FILLING: In a saucepan, mix all the ingredients and heat over medium heat. Stir regularly until the egg yolk sticks and the liquid forms a solid mass. Remove from the heat and pass through a coarse mesh sieve.
The sieved mass can then be filled onto the cake base. Then place in the refrigerator for 2-3 hours.
For decoration when serving, lemon slices and fresh peppermint leaves as well as some icing sugar are suitable.