Adults will love these elegant cookies, made with a touch of brandy. And they're great for a Hanukkah party.
Prepare the Cookies: Pulse flour, granulated sugar, and salt in a food processor until combined, 3 to 4 times. Add butter, and pulse until mixture resembles coarse sand, 5 to 6 times. Add egg yolks and brandy; process until clumps begin to form, 30 seconds to 1 minute. Turn mixture out onto a lightly floured work surface; knead until dough comes together, 3 to 4 times. Divide dough in half; shape each half into a 6-inch disk. Wrap each disk with plastic wrap, and chill 1 hour.
Preheat oven to 350°F. Let 1 dough disk stand at room temperature 10 minutes. Unwrap dough disk, and roll to 1/4-inch thickness on a lightly floured surface. Cut with a 3 1/2-inch snowflake-shaped cutter, rerolling scraps once. Place cookies 2 inches apart on parchment paper-lined baking sheets.
Bake in preheated oven until set and beginning to brown on edges, 9 to 10 minutes, switching pans top rack to bottom rack halfway through baking. Cool on pans 2 minutes; remove cookies to wire racks, and cool completely, about 20 minutes. Repeat process with remaining dough disk.
Prepare the Icing: Beat powdered sugar, meringue powder, and 2 tablespoons of the water on medium speed in a medium bowl until well combined, 3 to 4 minutes. Add up to 1 tablespoon water, 1/4 teaspoon at a time, until desired consistency is reached. Add food coloring, 1 drop at a time, and beat until frosting is desired color. Spread icing on cookies, and sprinkle with sparkling sugars.