In a large mixing bowl, mix the butter and sugar together on medium speed for about 1 minute until creamy.
Add the egg yolk, vanilla extract, almond extract and salt, and mix until well combined. While mixing on low, gradually add in the flour a little bit at a time and mix just until combined. Scrape down the bowl as needed during mixing to ensure everything is combined evenly.
Scoop a 1 tablespoon-sized portion of the dough and roll it into a ball.
Place the ball on a parchment paper-lined sheet and press your thumb or the back of a 1/4 teaspoon measuring spoon into the center of the ball to create a thumbprint.
TIP: Gently wiggle as you press to help prevent any cracks. If any cracks form, press them gently and smooth the surface. Repeat until all of the cookies have been formed.
To form a heart shape, use your pinky finger or the handle of a small spoon to press a V shape into the balls. If the heart shape loses definition during baking, immediately press the spoon handle back into the warm cookie to redefine the shape.
Optional: Transfer the cookies to the freezer to chill for 30 minutes. You can skip this step, but this will help keep the cookies from spreading and also improves their overall texture.
Preheat the oven to 350℉.
Line two large baking sheets with parchment paper.