Holiday dessert platter without a Linzer cookie is a travesty. It's like Easter without a bunny, Halloween without a jack-o'-lantern, Valentine's Day without chocolate. In short, Linzer cookies are necessary come December. Not only are they quite beautiful-the jam windowpane feature is all shimmery elegance-but the taste is always pleasing. Simple. Addictive.
Put the almonds and 1/4 cup of the sugar in the bowl of a food processor and pulse until the almonds are finely ground.
In a large bowl, whisk together the flour, unsweetened cocoa powder, baking powder, and salt. Set aside.
In the bowl of a standing mixer fitted with the paddle attachment, beat the butter and remaining 1/4 cup sugar until light and fluffy. Add the egg, egg yolk, and almond extract and beat until incorporated. Scrape down the sides and bottom of the bowl and add the flour mixture in three parts, alternating with the almond mixture, beginning and ending with the flour mixture. Scrape down the sides and bottom of the bowl one more time and then mix again.
Turn the dough out (it will be tacky) onto a lightly floured surface and bring it together with your hands. Form the dough into two disks and wrap them tightly in plastic wrap. Refrigerate for at least 3 hours or overnight.
Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper.
Unwrap one dough disk and place it on a lightly floured surface. Roll the dough into a round 1⁄8 inch (3 mm) thick, flipping and lightly sprinkling it with flour as needed so it doesn't stick. Using a 2 1/2-inch (6-cm) round cookie cutter, cut the dough and transfer the pieces to the prepared baking sheets, leaving about 1 inch (2.5 cm) of space around each cookie. Extra dough scraps can be refrigerated and rerolled, if desired. Continue the process with the remaining dough disk, and distribute the pieces equally between the two trays. Freeze the trays of cookies for 5 minutes.
If you like, you can bake the windowpane cutout scraps as well. Line one more baking sheet with parchment (if you don't have another baking sheet, you can place them on a large platter or plate lined with parchment until the sheet is free). Remove one sheet of dough from the freezer. Make the windowpane cutout: Working quickly, using a small cookie cutter (round, or heart- or starshaped, about 1 inch/2.5 cm in diameter), cut out shapes directly in the middle of each round of cookie dough. Place the cutout shape scraps on the last sheet or platter, if desired. Set aside. Remove the other sheet from the freezer, but leave the cookies intact. (In total, only half of your cookies should have cutouts.)
Bake the cookies, rotating the sheets halfway through the baking time, until they are set, 8 to 10 minutes. Place the baking sheets on wire racks to cool for 5 minutes. Then, using a spatula, transfer the cookies to the wire racks to cool completely. (If you reserved your cutout shape scraps on a platter, transfer them to one of the empty baking sheets and bake until set, 6 to 8 minutes. Again, place the baking sheet on a wire rack to cool for 5 minutes, then transfer the cookies to the wire rack to cool.)
Flip the cookies that are wholly intact (with no cutout) and spread an even layer of jam, about 1 teaspoon, over the cookie bottom. Dust the cookies with the cutout with a little confectioners' sugar, then place them directly over the jam-covered cookies. Dust the cutout shapes with confectioners' sugar as well, to eat alongside the assembled linzers. Allow the cookies to set for about 10 minutes before serving.
How to store: The cookies can be stored in an airtight container at room temperature for up to 4 days.