Preheat the oven to 350 degrees Fahrenheit. Line two baking sheets with parchment paper.
Prepare the dry ingredients. In a medium bowl, whisk together the flour, finely ground Earl Grey tea, dried lavender flowers, baking powder, baking soda, and salt. Set aside.
Cream the butter and sugar. In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and sugar on medium speed until light and fluffy, about 2-3 minutes. I always stop once and scrape down the sides of the bowl with a spatula and continue mixing.
Add the wet ingredients. Add the egg and vanilla. Beat until combined. Scrape down the sides and bottom of the bowl as needed.
Add the dry ingredients. Add the flour mixture and beat on low until just combined.
Portion and shape the cookies. Using a medium-sized cookie scoop (I used #40 ~2 Tablespoons), scoop balls of dough onto the prepared baking sheets. Place the cookies 2-3 inches apart. I like to put 8 on each sheet, staggering the cookies. Roll each scoop of dough between your hands to form a ball then place the ball back on the baking sheet.
Bake. Bake one pan at a time for 11-13 minutes or until the edges are just set but the centers are still gooey. Be careful not to overbake! This will keep your cookies super soft. 12 minutes is perfect for my oven.
Cool. Remove the pan from the oven and let the cookies cool on the baking sheet for 5 minutes. Transfer the cookies to a wire cooling rack and cool completely.