In a large bowl, add the softened butter and powdered sugar.

Use a spatula to mix until there's no dry sugar, then beat with an electric mixer until light, fluffy, and pale in colour.

Add the egg white in two batches, beating well after each addition until fully incorporated and smooth. The mixture should look creamy with no separation.

Sift the cake flour into the mixture, then add salt and the finely ground Earl Grey tea.

Gently fold everything together with a spatula until just combined and no dry flour remains. Avoid overmixing.

Transfer the dough into a piping bag and pipe your desired shapes onto a lined baking tray. Pipe slightly taller ridges for better definition. Chill the tray briefly in the fridge to help the cookies hold their shape.

Preheat the oven to 160°C. Bake the cookies on the middle rack for about 18 minutes, until the edges are lightly golden and the cookies are set.

Remove from the oven and let the cookies cool completely on a wire rack. They will become crisp and buttery as they cool.