Toast hazelnuts at 350°F (175°C) for 8-12 mins. Rub in a towel to remove skins. Cool completely, then grind into a fine meal in a food processor.

In a mixer, cream softened butter, granulated sugar, and brown sugar until light and fluffy, about 2-3 minutes.

Beat in the egg yolk, vanilla extract, and almond extract until combined.

In a separate bowl, whisk together the ground hazelnuts, flour, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing on low until just combined. Cover and chill dough for at least 1 hour.

Preheat oven to 350°F (175°C). Line baking sheets with parchment paper. Place egg white in one bowl and powdered sugar in another.

Roll dough into 1-inch balls. Dip each ball in egg white, then roll in powdered sugar. Place 2 inches apart on baking sheets.

Make a deep indentation in the center of each cookie with your thumb or the back of a spoon.

Bake for 12-15 minutes until set. Redefine indentations if needed right after baking. Cool on sheet for 5 mins, then transfer to a wire rack to cool completely.

Gently warm the jam and fill each cooled cookie's indentation. Let jam set before serving.