Preheat the oven to 350 F (175 C) and line baking sheets with parchment paper.
In a large bowl, cream together softened butter and granulated sugar until light and fluffy.
Beat in the egg yolks, one at a time, and stir in vanilla extract.
In a separate bowl, whisk together all-purpose flour and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until a soft dough forms.
Shape the dough into tablespoon-sized balls and place them on the prepared baking sheets.
Use your thumb or a small spoon to create an indentation in the center of each cookie.
Fill each indentation with a small amount of strawberry jam.
Bake for 10-12 minutes or until the edges are golden.
Allow the cookies to cool on the baking sheets for a few minutes before transferring them to a wire rack to cool completely.
