Add Earl Grey tea leaves to milk and microwave for 30 seconds.

Whip the butter until soft, then add sugar and whip until it turns ivory-colored.

Gradually add pre-whipped eggs in portions while continuing to whip.

Sift cake flour, baking powder, and salt into the mixture.

Mix gently until no dry flour is visible.

Add the cooled Earl Grey milk mixture and mix lightly.

Pour the batter into a parchment-lined pan.

Pipe a thin line of butter down the center of the batter.

Bake at 170°C for 35-40 minutes.

Transfer to a cooling rack and let it cool completely.