In a large bowl, cream the butter and sugar until fluffy.
Beat in egg yolks and vanilla extract.
Add salt and flour and mix until well combined.
Cover and chill the dough for at least 30 minutes (**see notes).
Preheat oven to 350 degrees F.
Line baking sheets with parchment paper or silicone baking mats.
Use a #40 cookie scoop to portion the dough and roll into a one-inch ball.
Place on the prepared baking sheet and gently press your thumb into each cookie. Can also use a tart shaper or the back of the cookie dough scoop.
Spoon ½-1 teaspoon jam into each cookie.
Bake for 12-14 minutes or until slightly firm and a light golden brown color.
Remove from oven and cool on a wire rack.
Notes
The cookies will be flatter if you don’t refrigerate the dough.
The dough can be chilled longer than 30 minutes and up to 3 days in the refrigerator. If chilling longer than 30 minutes, allow the dough to come to room temperature and work the dough in your hands to make it easier to roll into balls.
Don’t press too far down into the cookie - you don’t want to hit the bottom.
We recommend using a high quality jam. Can use other jam flavors - red raspberry, apricot and blackberry are a few of our favorites.
Do not use jelly - it’s too thin.
Cooled cookies can be dusted with powdered sugar or drizzled with a simple glaze.
Store cooled cookies for up to 3 days in an airtight container on the counter. If stacking them, use a piece of parchment paper between the layers.