1
In the bowl of a food processor, combine flour, baking powder, salt, and tea leaves. Pulse until tea leaves are finely ground, 6-pulses.

2
In the bowl of a stand mixer fitted with a paddle attachment, beat together butter and sugar until fluffy, about 4 minutes. Beat in vanilla, followed by egg. Add dry ingredients to bowl and mix just until dough comes together. Wrap dough in plastic wrap and chill in refrigerator for 1 hour.

3
Adjust oven racks to upper and lower middle positions and preheat oven to 350°F. Line two baking sheets with parchment paper.

4
Lightly flour a clean work surface. Roll dough out to 1/4-inch thickness. Cut out cookies with cutter of your choice, then transfer to prepared baking sheet. Bake until cookies are just golden at the edges, about 12 minutes. Let cool 5 minutes then transfer to a wire rack to finish cooling.

See more at http://www.seriouseats.com/recipes/2014/03/earl-grey-tea-cookies.html