In the bowl of a standing mixer fitted with a paddle attachment, cream together the butter and sugar for about a minute until light and incorporated. Add the egg yolks and extract, then mix for another minute, scraping the sides of the bowl occasionally.

Add the flour and salt, and mix until the dough comes together.

Line a large baking sheet with parchment paper. Using a one tablespoon-size cookie scoop, scoop the cookie dough onto the baking sheet. Roll each ball of cookie dough between your palms until smooth.

Using either your thumb or the back of a round ½ teaspoon, gently make an indent in the center of each cookie. Place the baking sheet in the freezer for 20 minutes.

Preheat your oven to 350 degrees. Bake for 12-14 minutes or until the edges are lightly golden.

Remove from oven and let cool on the baking sheet for 5 minutes. Fill each indent with about half a teaspoon of your favorite jam. Transfer to a wire rack to cool completely.