What you'll need for these cookies...
Sand butter and dry ingredients together.
Stir in yolks and vanilla to form a smooth dough.
Chill dough for 30 minutes.
Roll to 1/8" thick and cut out 2" rounds.
Pair cookies and cut heart-shaped center out of half the dough rounds.
Add jam to each bottom cookie, then top with a heart-cut-out dough round.
Bake until golden brown on the edges, with bubbling jam.