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

In a large bowl, cream together the softened butter, sugar, and brown sugar for 1 minute using an electric handheld mixer or a stand mixer fitted with the paddle attachment on high speed.

Add the egg yolk and vanilla and continue creaming until fluffy. Add the flour and mix at low speed just until fully incorporated.

Scoop the cookie dough into 1 tablespoon-sized portions and roll well to form smooth, uniform balls. Place on the prepared baking sheet, leaving 2 inches between each cookie for spreading room.

Make an indent in each cookie dough ball using either your thumb or I like to use a well-floured round ½ teaspoon measuring spoon to do this. Fill each indent with apricot jam.

Bake cookies, one pan at a time, in the preheated oven for 10-12 minutes or until slightly golden on the bottoms and the jam should be bubbly. Let cool for at least 10 minutes on the baking sheet. Bake the remaining cookies. Enjoy!