German Hazelnut Shortbread Triangles

Step 1

In a medium bowl, cream together 0.5 cup softened unsalted butter and 0.25 cup granulated sugar using an electric mixer or by hand with a wooden spoon, beating until pale and fluffy, about 3 minutes. The mixture should look light and almost mousse-like.

Step 2

Add 1 large egg yolk and 0.5 teaspoon vanilla extract to the butter mixture and beat until fully combined, scraping down the sides of the bowl with a rubber spatula.

Step 3

In a separate small bowl, whisk together 1.5 cups all-purpose flour and 0.25 teaspoon fine sea salt. Gradually fold the dry ingredients into the wet ingredients using the spatula until a shaggy dough just comes together — do not overmix or the shortbread will be tough.

Step 4

Form the dough into a flat disk, wrap it in plastic wrap, and refrigerate for at least 30 minutes while you preheat your oven. This prevents the dough from shrinking in the oven.

Step 5

Preheat your oven to 375°F (190°C). Line a 9-by-13-inch baking sheet with parchment paper.

Step 6

Remove the chilled dough from the refrigerator and place it on a sheet of parchment paper. Roll it out into a thin 9-by-13-inch rectangle, about 1/8 inch thick — you should almost be able to see the parchment through it. This thin base ensures an even, crispy texture.

Step 7

Slide the rolled-out dough (still on parchment) onto your prepared baking sheet. Spread 0.5 cup seedless raspberry jam evenly across the entire surface using an offset spatula or the back of a spoon, leaving a very thin 1/4-inch border around the edges.

Step 8

In a small bowl, whisk together 1 large egg white (not the yolk) and 0.25 cup granulated sugar until the sugar dissolves and the mixture becomes foamy, about 1 minute. This is your binder for the nuts.

Step 9

Stir 1.25 cups finely chopped roasted unsalted hazelnuts and 0.25 teaspoon vanilla extract into the egg white mixture until you have a thick, chunky paste.

Step 10

Spread the hazelnut topping evenly over the jam layer in a thin, even coat — an offset spatula works best. You want the nuts to adhere to the jam and egg white base.

Step 11

Bake on the middle oven rack for 20-25 minutes, until the shortbread is golden at the edges and the hazelnut topping is light golden brown and fragrant. The center may still look slightly soft — this is correct, as it will firm up as it cools.

Step 12

Remove the baking sheet from the oven and let it cool to room temperature, about 30 minutes. This is crucial — cutting warm pastry will cause it to crumble.

Step 13

Once cooled, trim a thin border from all four edges of the pastry using a sharp chef's knife. Wipe the knife clean between cuts to prevent dragging nuts and jam. Cut the pastry into 12 diamond-shaped pieces by first cutting lengthwise into 3 vertical strips, then cutting each strip at diagonal 45-degree angles to form diamonds.

Step 14

Serve at room temperature. Store leftovers in an airtight container at room temperature for up to 3 days — the shortbread will stay crisp and the hazelnut crust will remain crunchy.