Blend together the soft butter, powdered sugar, vanilla and the egg yokes until it is fluffy.
Add ground almonds and flour and knead into a smooth dough.
Let dough chill in fridge for 1hr.
Roll out the dough about 3mm thick. Cut out an even number of cookies. Now take half of them and cut out the little heart. Put cookies on a baking tray covered with baking paper.
Bake for 6-8min at 350°F/180°C.
While the cookies are cooling down, heat the jam. Put jam on all BOTTOM halfs and stick the top halfs on top. Dust with powdered sugar.