No Scandinavian Christmas celebration would be complete without Swedish Overnights. Also called Swedish Heirloom Cookies, Swedish Overnights share similar ingredients to Mexican Wedding Balls. These cookies can be dusted with powered sugar, or in this case, colorful sprinkles for a festive touch. Leslie inherited this recipe from her mother’s family and she loves baking these cookies every Christmas. We hope you enjoy them, too.Check out our video to follow Leslie’s simple step-by-step instructions for preparing these cookies!Swedish OvernightsClick here to print this recipe!Ingredients 8 ounces (2 sticks) unsalted butter, at room temperature1 cup powdered sugar, sifted1 egg, separated1 teaspoon pure vanilla extract2 1/4 cups unbleached all-purpose flour1 cup finely chopped walnutsCrystal sugar in your favorite colorsPrepare this dough 1 day before baking.Makes 3 dozen cookies1. Combine butter and sugar in the bowl of your stand mixer. Using the paddle attachment, mix on low speed for about 30 seconds. Increase speed to medium and mix for another 5 to 7 minutes, or until the mixture is smooth and pale in color. Add the egg yolk and vanilla extract and mix for about 30 seconds. Scrape down the sides of the bowl with a rubber spatula and mix for another 30 seconds, making sure egg and vanilla are thoroughly incorporated. Remove bowl from mixer and scrape down the sides of the bowl again.2. Using a rubber spatula, fold half of the flour into the dough. After the first batch is fully incorporated, fold in the other half and continue folding until all of the flour has been absorbed, 1 to 2 minutes.3. Pull dough from the bowl and onto a floured surface and divide it in half. Roll each half into a log about 1 1/2 inches thick, and place the logs on separate pieces of parchment paper. (The parchment paper needs to be at least 4 inches longer than the logs.) Brush the logs with the egg white, then scatter half of the walnuts over each log. Roll the logs back and forth until they are completely coated in nuts. Roll each log up within its parchment paper. Finish by twisting the ends of the paper to create a seal. Chill logs in the refrigerator over night.4. Preheat oven to 325ºF. Line 2 rimmed baking sheets with parchment paper.5. Unwrap the logs and using a sharp knife, cut them into 1/2-inch-think coins. Place the cookies on the prepared baking sheets, leaving 1 inch between each cookie. Brush the top of each cookie with a tiny bit of water and sprinkle festive sugar crystals on top.6. Bake on center rack of oven, 1 sheet at a time, for 20 to 25 minutes. To help the cookies bake evenly, rotate the baking sheet every 4 minutes or so. The finished cookies will be golden brown on the edges and pale in the center. Let cookies cool completely on the baking sheet. They can be stored in an airtight container for up to 1 month at room temperature.