Delicious shortbread cookies filled with jam or chocolate that you can find in every bakery in Rome. My absolute favorite childhood treat!
100 g butter, unsalted, cold, cubed
50 g granulated sugar
50 g vanilla sugar (or 100 g granulated sugar total)
200 g flour type 00 or unbleached all-purpose flour
1 large egg
icing sugar for topping
jam for filling