Preheat the oven to 350 deg. Line baking sheets with parchment paper.

In a large bowl, cream the butter and sugar until combined. Mix in yolks, vanilla and salt until combined. Mix in flour.

Scoop cookies with a 1 tablespoon scoop onto prepared trays. With a rounded teaspoon, indent each ball. Spoon ½ a teaspoon of jam into each indention.

Bake for 12-14 min or until cookies are set and lightly browned. Remove from the oven and let them cool for 10 min. Transfer them to a wire rack to cool completely. Store in an airtight container.