Preheat oven to 350F. Line 9x13 baking sheet with parchment paper.
Place your tea leaves in a food processor or spice grinder. Pulse until you get a ground consistency not powdery. Transfer to a bowl and add in flour and salt.
In a separate bowl, beat your butter using a hand mixer at medium speed. Stop and add in 2 1/2 cups of confectioner's sugar + vanilla extract and beat again on low speed. Once combined increase the speed and beat until you get a very smooth consistency. Add in your flour mixture and mix carefully again using a wooden spatula.
Using a spatula (or clean hands) bring your dough together until you can form a clean ball.
Scrape your dough into the pan and cover with plastic wrap. Gently press the dough evenly into the pan. Using a tooth pick, poke holes - spaced by 1" - into your dough for decoration. Discard plastic and bake in middle rack for 40-45 minutes, or until the edges are lightly golden.
Take the pan out of the oven and allow to cool for about 20 minutes. Gently transfer out of the pan and cut into little squares. My preferred size is 2"x1". I cut out the outer pieces and stored them in a Tupperware.
Make your glaze (optional):
Whisk 1 cup of confectioner's sugar with 3 tbsp of whole milk. Drizzle over cooled shortbread. To finish it off, drizzle a little caster sugar on top. Enjoy <3
Stand mixer: making this recipe in a stand mixer is a lot easier and lot less messy. So if you have one, I highly recommend that you use it.