Technicolor Cookies

Begin by making the cookies. Whisk together the flour, cinnamon, ginger, cardamom, baking powder, and salt in a medium-sized bowl.

Combine the butter, granulated sugar, orange zest, vanilla extract, and egg in a large bowl using an electric mixer set to medium speed. Add the flour mixture to the butter mixture and beat until they are well combined.

Place a 12-by-16-inch sheet of parchment paper on your work surface. Put the dough on top and cover it with another piece of parchment. Roll the dough into an even ¼-inch-thick rectangle, ensuring the edges are squared off. Transfer the dough, still sandwiched between the parchment layers, to a rimmed baking sheet and refrigerate it until it becomes cold and firm, about 30 minutes.

Next, prepare the royal icing. In a large bowl, combine the powdered sugar and meringue powder. Add ⅔ cup of water and beat the mixture with an electric mixer set to medium speed until it becomes thick and glossy approximately 7 minutes. To check the icing's consistency, try drizzling it over itself—it should take about 10 seconds to reincorporate. Add more water, 1 teaspoon at a time, until you achieve that desired consistency.

Now, divide the icing into 5 bowls and tint 4 as desired, leaving one bowl white. Cover these bowls and let them sit at room temperature for 30 minutes.

Preheat the oven to 350 degrees Fahrenheit and line two baking sheets with parchment paper.

Retrieve the chilled dough from the refrigerator and, working swiftly, cut it into rectangles measuring 1 by 2.5 inches. If the dough is still cold, separate the rectangles and place them on the prepared baking sheets, leaving about 1/4 inch of space between each. If the dough has warmed up, chill (or freeze) it until it's cold enough for baking.

Bake the cookies, rotating the sheets halfway through, until they turn a golden brown, typically taking 10 to 12 minutes. Transfer the cookies to a cooling rack and let them cool completely for approximately 30 minutes. Arrange the cookies on the rack with their sides touching, forming rows of 8.

Place another rack over a parchment-lined sheet. Take a small (4-inch-diameter) bowl and spoon a bit of each colored icing into it, creating several parallel bands of colored icing. (Remember to cover any unused icing.) Pour the icing over the cookies in thin ribbons, moving from left to right, then right to left, and back again, filling in any gaps until you've used up all the icing. Repeat this process with more icing as needed. Immediately and carefully separate each cookie using an offset spatula and transfer them to the clean rack.

Allow the cookies to sit at room temperature, uncovered, until the icing sets, which typically takes at least 6 hours.