Place the Earl Grey tea leaves in a spice grinder or clean coffee grinder. Process until the leaves are a fine powder. Set aside.
In a large bowl, cream together the softened butter and granulated sugar until light and fluffy. This takes about 3 minutes.
Beat in the vanilla extract and the ground Earl Grey tea until fully combined.
In a separate bowl, whisk together the flour and salt. Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined into a soft dough. Do not overmix.
Shape the dough into a disk, wrap it in plastic wrap, and chill in the refrigerator for at least 30 minutes. This step helps prevent spreading.
Preheat your oven to 325 degrees Fahrenheit (160 degrees Celsius). Line baking sheets with parchment paper.
Roll the chilled dough out on a lightly floured surface to about 1/4 inch thickness. Use cookie cutters to cut out desired shapes.
Place the cutouts onto the prepared baking sheets. Prick the tops of the cookies a few times with a fork.
Bake for 12 to 15 minutes, or until the edges are set and very lightly golden. The cookies should remain pale.
Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
While the cookies cool, prepare the glaze: Whisk together the powdered sugar and lemon juice until smooth. Add more lemon juice, a few drops at a time, if the glaze is too thick.
Once the cookies are completely cool, drizzle or dip the tops into the lemon glaze. Let the glaze set before serving.
Notes
For the best bergamot flavor, use high-quality Earl Grey tea bags or loose leaf tea.
If you prefer a softer cookie, chill the dough for 1 hour instead of 30 minutes.
You can substitute the lemon glaze with a simple vanilla glaze or dust the cooled cookies with powdered sugar for a simpler finish.
These buttery tea cookies store well in an airtight container at room temperature for up to one week.