Beat the soft butter and sugar until frothy. Add the egg, the zest and the juice of the lime and salt. Only when everything is very well mixed, gently fold in the flour. (Do not mix too much with the flour, otherwise you will get hard biscuits.)
Finished.
Shape the dough into 3cm thick rolls, roll in crushed sugar and wrapped in wax paper at least! Put in the fridge for an hour.
When the rolls are hard, cut into ¾ cm thick slices and bake in the preheated oven for 12-15 minutes. The edges should at most be slightly golden brown.
Regular sugar melts during baking. Hail sugar stays as it is !!
The original recipe wanted vanilla instead of lime. Since I didn`t have any vanilla in the house, I did have a lime.
My kids are crazy about it even though it really is an adult cookie.