These cookies are a nostalgic favorite with a grown-up twist. The combo of toasted hazelnuts and raspberry jam is simple but elegant. Each bite is soft, crisp and fruity.
Preheat oven to 325°F. Prepare baking sheets with parchment paper and set aside.
Add butter and ½ cup sugar in the bowl of a stand mixer fitted with the paddle attachment.
Mix on medium speed until the dough is pale and fluffy.
Add the lightly beaten egg yolks and the vanilla. Mix well.
Reduce speed to low and then add flour. Mix until just combined.
Refrigerate the cookie dough for 2 hours.
Stir together toasted hazelnuts and the remaining 2 tablespoons sugar in a small bowl.
Roll dough into 1 inch balls. Dip the balls in the lightly beaten egg whites, then into the hazelnut/sugar mixture.
Space the dough balls 1 inch apart on the prepared baking sheets.
Press down the center of each ball with your thumb.
Optional: If you want to fill the cookies before baking, that's fine, but only fill them about 3/4 full so they don't overflow during baking (I fill mine after).
Bake cookies for 10 minutes. Remove from oven. Press down centers again with the end of a wooden spoon or a small spoon (if not filled with jam).
Return the cookies to the oven. Bake cookies until golden brown which should be 7 to 10 minutes more.
Let the cookies cool slightly on the baking sheets on wire racks. Fill each cookie center with jam and then let cool completely on the wire racks.
Notes
Chill the dough: This helps the cookies hold their shape during baking. Toast the hazelnuts: Toasting brings out more flavor and crunch. Use parchment paper: It prevents sticking and makes cleanup easy.