In a stand mixer with paddle attachment, cream together softened butter for about 5 minutes on medium-high speed until light and fluffy. Scrape down sides occasionally to ensure even mixing.
Add in your sugar and salt and continue mixing on medium-high speed for about 5-7 minutes, scraping down sides occasionally to ensure all sugar and salt is incorporated into the butter mixture.
Add in vanilla extract and lemon zest.
If you have loose tea leaves, make sure to ground them up into fine powder using either a mortar and pestle or a food processor before adding to the mixture. If you have earl grey tea bags, you can just cut open the tea bags and dump them into the mixture.
Finally, add in your all purpose flour in thirds to ensure flour is evenly incorporated into your mixture. Reduce the speed down to low and allow to mix just until all flour is incorporated into the butter. Avoid overmixing.
Once there are no dry lumps left in your bowl, turn the dough mixture onto some saran wrap and shape it into a large rectangular sheet. You can sandwich the dough between two saran wrap and roll it out with a rolling pin to avoid dough from sticking. Dough should be half inch thick. Then, refrigerate for at least 2 hours to allow dough to set.
After 2 hours, take the dough from fridge and allow to rest at room temperature for about 5 minutes to allow dough to soften a bit to allow for you to use your cookie cutters to cut out shapes. Once you’ve cut out all the shapes, place them in the on your baking tray lined with parchment paper/silpat and put in fridge to chill for 5 minutes. Dough should be hard before baking.
Preheat oven to 325F in the meantime. Once ready, bake the shortbread cookies for 17-20 minutes, rotating half way to ensure even baking. Bake until the cookies are slightly golden on the sides. The cookie should not be brown so do not overbake! If you use a convection oven, your baking time may be reduced.
Allow to chill for 15 minutes before serving. This makes about 40 small (2 inch) cookies.