Start by beating the butter and sugar together in a large bowl until light and creamy.
Add the egg yolks and vanilla extract, mixing until smooth.
Gradually stir in the flour and salt until a soft dough forms.
If it feels too soft, chill it in the refrigerator for 20–30 minutes to make shaping easier.
Roll the dough into 1-inch balls and place them on a baking sheet lined with parchment paper.
gently press your thumb into the center of each ball to make a small indentation.
Spoon about ½ teaspoon of jam into each indentation.
Bake the cookies for 12–14 minutes, or until the edges are lightly golden.
Let them cool on the baking sheet for 5 minutes before transferring to a wire rack.
