01 -
Preheat oven to 325°F (160°C). Line 2 baking sheets with parchment paper.
02 -
In a food processor, pulse the flour, sugar, and salt together to combine thoroughly.
03 -
Add half of the butter pieces to the food processor and pulse a few times. Then add the remaining butter and continue pulsing in short bursts until the dough comes together.
04 -
Divide the dough into 4 equal portions and place each in a separate bowl. Add different gel food coloring to each portion and mix well until the color is evenly distributed throughout the dough.
05 -
Lay out a sheet of plastic wrap on your work surface. Place each colored dough in strips side by side, arranging them from lightest to darkest color. Roll them together to form a cylinder shape, then cut one end to create a clean edge.
06 -
Place the dough cylinder into a piping bag fitted with a large star tip.
07 -
Pipe cookies onto the prepared baking sheets, leaving space between each cookie to allow for slight spreading during baking.
08 -
Bake in the preheated oven for 25 minutes, rotating the pans halfway through the baking time. The cookies should be set but not browned.
09 -
Allow the cookies to cool completely on a wire rack before decorating.
10 -
Place the white melting wafers in a microwave-safe bowl. Microwave in 10-second intervals, stirring between each interval, until completely melted and smooth.
11 -
Dip the piped edge of each cookie into the melted white chocolate, then immediately sprinkle with rainbow nonpareils before the chocolate sets.
12 -
Place the decorated cookies on parchment paper and allow the chocolate to completely set before serving or storing.