Step 1In a small sauté pan, toast the tea over medium-low heat until fragrant, about 2 minutes, then grind with a spice grinder to a coarse powder.
Step 2Cream together the butter and sugar, then add the egg and mix well. Add the ground tea and flour, mix well, then wrap the dough in plastic and refrigerate until firm, 15 to 30 minutes.
Step 3Remove the dough and roll it into a log approximately 11/2 inches in diamater. Wrap in plastic again and refrigerate or freeze until very firm, about 1 hour.
Step 4Heat the oven to 350 degrees. Cut the dough into rounds a little thicker than 1/4 inch. Place them on a parchment-lined baking sheet, spacing them about 1 inch apart. Bake until the cookies are set and lightly golden underneath, 15 to 20 minutes.