Measure out tea and empty into a small bowl. If using tea with larger pieces, crush the tea leaves (using a spice grinder, mortar and pestle or a plastic bag and a rolling pin) for a finer consistency, with no large or woody pieces remaining.
In a large mixing bowl, combine the Earl Grey tea and flour, whisking together to incorporate the tea throughout the flour.
Add the salt and confectioners’ sugar. Whisk until well blended.
In the bowl of an electric mixer fitted with the paddle attachment, cream the butter for 30 seconds. Add the dry ingredients and mix on low speed. The dough will slowly form as the beater turns. When the dough is well formed it should not be sticky, and it will be thick and clump on the beater.
Remove the dough to a piece of plastic wrap and pat into a disk. Refrigerate for 10 minutes.
Dust a work surface with flour. Remove the dough from the refrigerator and cut in half. Place a half on the dusted work surface. Dust the dough and a rolling pin lightly with flour. Roll the piece to a little greater than 1/2-inch thickness.
Dust silicone mold with flour using a pastry brush loaded with flour and liberally flour the silicone mold. Turn the mold over and tap out excess flour.
Lay the rolled dough over the silicone mat and press the dough into the cavities with your fingers. Use the rolling pin to roll the dough flat to about 1/4 inch. Flip the mold over onto a parchment sheet and gently peel the mold away from the dough revealing embossed design. Cut away the excess dough from the edges and transfer the molded piece to the freezer to stiffen completely (about 10 minutes). Repeat the molding process with the remaining dough.
Preheat the oven to 300F.
Remove the frozen dough pieces from the freezer and cut into desired size cookies ( 2 x 2 inch pieces or 4 x 2 inch shapes ). Bake the cookies from their frozen state for about 20 minutes, or until they are very slightly puffed and have a matte surface. The cookies should be pale with the bottom edges very light golden in color.
Let the cookies cool on the pans until they are firm enough to move, about 10 minutes. Remove to a wire rack to cool completely. Keep shortbread in an airtight container at room temperature for up to 6 days.