Begin by combining unsalted butter and granulated sugar in a large bowl. Using a hand mixer, beat them together until the mixture becomes lighter in color and fluffy, which should take about 3 to 4 minutes. This step is crucial as it incorporates air into the mixture, resulting in a light cookie texture.
Next, beat in the large egg, pure vanilla extract, almond extract, and lemon or orange zest (if you're using it) until everything is well blended. Your batter should have a smooth consistency.
In a separate bowl, whisk together the all-purpose flour and kosher salt. This helps to evenly distribute the salt throughout the flour.
Slowly add the flour mixture to the butter mixture all at once, mixing on low speed until just incorporated. Be careful not to overmix; you want a dough that holds together but isn’t tough.
Prepare your workspace by laying out a baking sheet with parchment paper and sprinkling a little flour on top. This will prevent your dough from sticking.
Divide the dough into two equal portions (more if doubling the recipe). Shape one portion into a disc. Remember to keep your hands lightly floured to avoid sticking.
Place the disc on the floured paper and roll it out gently into a rectangle or oval that is about ¼ inch thick. Use cookie cutters to cut out shapes from the dough.
Transfer the cut-out cookies to the prepared baking sheets. Make sure to space them apart to allow for spreading during baking.
Cover the baking sheets tightly with plastic wrap and refrigerate the cookies for at least 2 hours, or overnight if possible. This helps the cookies maintain their shape while baking.
Preheat your oven to 350°F (175°C). Once the cookies are chilled, space them out on parchment-lined cookie sheets and bake for about 10 minutes, or until the edges just begin to turn golden brown.
Remove the cookies from the oven and let them cool on the baking sheet for a few minutes before transferring them to a cooling rack. This is important so that they don’t break.
Once cool, it’s time for the fun part—decorating! In a large mixing bowl, add powdered sugar and turn the hand mixer to the lowest speed.
In a separate measuring cup, mix together corn syrup, water, and the remaining almond extract. Slowly drizzle in ½ cup of this mixture over the powdered sugar while mixing until smooth. The glaze should resemble sweetened condensed milk in consistency.
Divide the glaze into smaller bowls for coloring. Start with a drop of food coloring and swirl it through the glaze. Be cautious not to overmix, as you want the marbling effect.
To glaze a cookie, hold it by the edges and dip the top in the glaze. Allow any excess glaze to drip off into a second bowl for a few seconds before setting the cookie on a cooling rack.
Let the glaze dry completely before storing the cookies in an airtight container. For best results, let them dry for 12 to 24 hours.