Line two 13×9 baking sheets with well-fitting parchment paper.

In a medium bowl, whisk together the flour, cornstarch, and salt. Set aside.

In the large bowl of a stand mixer or with a hand mixer, cream the butter with the sugars starting on medium speed and gradually increasing to medium-high for 2-3 minutes until it's lighter and creamy.

Scrape down the bowl, then mix in the egg yolk, vanilla, and almond extract.

Set the mixture to low and slowly add in the dry ingredients into the wet ingredients. Scrape down the bowl as needed.

Using a 1 tablespoon-sized dough scoop, make dough balls, rolling them as smoothly as possible between your palms.

Place each dough ball 2 inches apart onto the prepared baking sheet. Gently press the heart shape into the top of the cookie dough with a pinky finger.

Place the cookie sheet into the freezer for 30 minutes or the refrigerator for 1 hour.

Pull the baking sheets from the freezer and preheat the oven to 375°F.

Put the fruit preserves into a small microwave-safe bowl and heat for 10-15 seconds until it's a little runny. Using a 1/4 teaspoon or a very small spoon, fill the heart indent to the brim with about 1/2 teaspoon of jam.

Bake each tray of cookies for 10-12 minutes, until the cookie edges just start to turn golden brown.

Let cookies cool on the cookie sheet for 5 minutes before transferring them to a cooling rack.