In the bowl of a food processor, combine the tea, butter and sugar. Pulse until the tea is finely chopped and the mixture is creamy. In a medium bowl, whisk together the flours, baking powder and salt; add to the food processor. Add a few drops of food coloring, if using, and process 1 minute. Turn the dough out onto a floured surface and knead until the dough is smooth and the color is even.
Form the dough into a 12-inch rectangular log. Wrap the dough in plastic and refrigerate until very firm, 4 to 5 hours.
Preheat the oven to 325 degrees F.
Transfer the dough to a cutting board and slice into 3/4-inch slices. Arrange the slices on a baking sheet and bake until slightly golden, 12 to 15 minutes. Transfer the cookies to a wire rack to cool completely.
This recipe was provided by professional chefs and has been scaled down from a bulk recipe provided by a restaurant. The Food Network Kitchens chefs have not tested this recipe, in the proportions indicated, and therefore, we cannot make any representation as to the results.