Thumbprint Heart Cookies with Jam

Use either a stand mixer with the paddle attachment, or a hand mixer.
Cream the softened butter & both sugars until just creamy, about 1 minute.
Add the egg yolks, vanilla extract, and salt to the mixing bowl. Beat until just combined, scraping down the sides of the bowl as needed.
Turn your mixer to low speed. Pour in your flour, a little at a time, until a dough is formed.
Prepare 2 large cookie sheets with parchment paper.
Grab 1 tablespoon of cookie dough (or 20 grams) and roll them into smooth balls in between your palms. Repeat with the rest of the dough, placing the dough balls onto the parchment-lined baking trays.
You can also use a mini cookie scoop to scoop same-sized portions and then roll each one by hand.
Use your pinky finger to create small indents in the middle of the dough that look like a hearts.
If any cracks form on the outside of the dough, you can either smooth them over with your hands by gently pressing the cracks together, or just re-roll the entire ball and start from scratch.
Chill in the indented cookies on the trays in the refrigerator until firm, for at least an hour.
Preheat your oven to 350℉.
Fill a pastry bag or Ziploc bag with the strawberry jam. Pipe the jam onto the heart shapes; the cookies should be full, but not overflowing.
Bake on the top rack of the oven for 13-15 minutes, until the edges just begin to turn golden brown.
Finally, remove them from the oven and cool completely on the pan.
Top with sifted powdered sugar on top and serve. Enjoy!