2 sticks butter, room temperature
1/2 cup sugar
2 egg yolks, room temperature
1 tsp vanilla extract
1/4 tsp kosher salt
2 cups all purpose flour
Beat the butter and sugar on high speed for 3 minutes. Separate eggs. Add yolks and vanilla to the butter mixture. Reserve the egg whites for another use.
Add the flour and salt into the mixture and mix until just combined.
Chill for at least 30 minutes. I have chilled for an entire day and let the dough warm up enough to roll into balls later.
Preheat the oven to 350oF. Line a baking sheet with a silpat. Roll out the cookies into 1 inch balls. Place the balls on the cookie sheets spaced a few inches away. Press down each ball to make a thumb print deep enough for the jam. Fill each indent with 1/2 tsp jam (of your choice).
Bake for 12 – 15 minutes or until slightly firm. Allow to cool for a few minutes before transferring to a wire rack.