½ cup (112 grams) white sparkling sugar, plus more for sprinkling
1 large egg (50 grams), lightly beaten
Instructions
In the bowl of a stand mixer fitted with the paddle attachment, beat butter and granulated sugar at medium speed until creamy, 2 to 3 minutes, stopping to scrape sides of bowl. Beat in extracts.
In a medium bowl, whisk together flour and salt. With mixer on low speed, gradually add flour mixture to butter mixture, beating until combined. Fold in nonpareils. (Dough will be rather soft at this point.) Divide dough in half. Shape each half into a 7-inch-long log (about 2 inches thick). Wrap each log in plastic wrap; holding ends of plastic wrap, roll log over work surface, creating a more rounded shape. Refrigerate until firm, about 2 hours. (See Note.)
Preheat oven to 325°F (170°C). Line 2 to 3 rimmed baking sheets with parchment paper.
In a large rimmed baking dish or plate, place sparkling sugar. Working with one dough log at a time, unwrap log, and brush outside with egg; roll in sparkling sugar. Working in batches and using a serrated knife, cut logs crosswise into ¼-inch-thick rounds, and place 1 to 1¼ inches apart on prepared pans; flatten rounds slightly so they lay flush on baking sheet. (If dough rounds crack when flattening, simply press and smooth back together.) Sprinkle tops with sparkling sugar.
Bake, one batch at a time, until edges are lightly golden, about 15 minutes. Let cool on pan for 5 minutes. Using a large offset or flat metal spatula, remove from pan, and let cool completely on wire racks. Store in an airtight container for up to 1 week.
Notes
Let dough that has been refrigerated for longer time spans stand at room temperature until slightly softened and easier to slice, 15 to 30 minutes.
Recipe by Bake from Scratch at https://staging.bakefromscratch.com/slice-bake-holiday-confetti-cookies/