In the bowl of a stand mixer fitted with a paddle attachment, beat together the butter and powdered sugar on medium speed for 2 minutes or until smooth and creamy.
1 ½ cups unsalted butter, 1 cup powdered sugar
Add the egg whites and beat for another minute. Add the vanilla extract and mix for a few seconds to incorporate.
2 egg whites, 1 teaspoon pure vanilla extract
Add the all-purpose flour and salt and beat on high speed for 2 minutes or until extremely smooth.
3 ½ cups all-purpose flour, ½ teaspoon salt
Fold in the almond flour and almond extract, mixing until incorporated.
1 cup almond flour, ¼ teaspoon almond extract
Wrap the cookie dough in plastic wrap and refrigerate for 30 minutes.
Once chilled, remove the dough from the refrigerator and unwrap. Preheat the oven to 350°F. Line 2 baking sheets with parchment paper. Set aside.
Cut out the base cookies. Roll out the dough into a rough rectangle about ¼-inch thick on a lightly floured surface. Using a 2-inch linzer cookie cutter without the circle center cutout attachment cut out 30 base cookies. Use a bench knife or spatula to remove the cookies from the floured surface and place ½ inch apart onto prepared baking sheets. (If you run out of room on your baking sheets, work in batches.)
Cut out the top cookies. Roll the remaining dough back into a ball. Roll out into a rough rectangle about ¼-inch thick. Place the center circle cutout attachment into the cookie cutter and cut out 30 top cookies. Remove the center cutout so that there is a hole in the cookie before carefully placing the cut-out cookie dough ½ inch apart onto prepared baking sheets. (If you run out of room on your baking sheets, work in batches.)
Bake the cookies for 10 minutes. Let cool on the baking sheet for 5 minutes, then transfer to a cooling rack to cool completely.
When cutting the cookies out to finish off the remaining dough, remember to cut a base cookie and top cookie. Continue rolling, cutting, and baking the cookies until all of the dough is used and all of the cookies are baked.
Assemble the cookies. Spoon about 1 teaspoon of jam onto the center of the base cookie (the cookie without the center cut out).
1 ⅓ cups jam
Press a top cookie (the cookie with the center cut out) directly on top making sure that the edges are aligned. This will cause the jelly to come up into the center of the cookie. If the center of the cookie is not filled with jam, you can spoon in a little extra jam to finish filling it. Repeat to make 30 total sandwich cookies.
Once all of the cookies are filled, use a fine mesh sieve to sprinkle powdered sugar over the cookies.
½ cup powdered sugar
Storage: Store cookies in an airtight container at room temperature for up to 3 days or in the refrigerator for up to 1 week.