Preheat your oven to 375°F (190°C).

Line baking sheets with parchment paper.

In a medium bowl, whisk together all-purpose flour, cornstarch, and salt. Set aside.

In a large bowl, cream unsalted butter, light brown sugar, and granulated sugar until light and creamy.

Add egg yolk, vanilla extract, and almond extract, and mix until well combined.

Gradually add the dry flour mixture to the wet mixture until just combined, being careful not to overmix.

Shape the dough into tablespoon-sized balls and place them on the prepared baking sheets.

Gently press a heart shape into the top of each dough ball to create an indentation for the jam.

Chill the cookies in the freezer for about 30 minutes or in the refrigerator for 1 hour.

Heat raspberry jam in a small saucepan over low heat until slightly runny.

Once dough is chilled, fill the heart indentations with warm raspberry jam, being careful not to overfill.

Bake the cookies in the preheated oven for 10-12 minutes, until the edges are golden brown.

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

Allow them to fully cool before serving.