01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - In a large bowl, cream together softened butter and granulated sugar until light and fluffy.
03 - Beat in egg yolks and vanilla extract until well combined.
04 - Add flour and salt; mix until a soft dough forms.
05 - Scoop tablespoon-sized portions and roll into balls. Place 2 inches apart on prepared baking sheets.
06 - Gently press an indentation into center of each dough ball using thumb or back of small spoon.
07 - Fill each indentation with about 1/2 teaspoon of jam.
08 - Bake for 13-15 minutes until edges are lightly golden.
09 - Let cookies cool on baking sheet for 5 minutes before transferring to wire rack to cool completely.