Mix the butter and powdered sugar until combined.

Add the egg yolk and vanilla extract, then mix well.

Sift the cake flour, almond flour, matcha powder, and salt into the mixture.

Mix until no dry flour is visible, using a cutting motion.

Shape the dough into a single mass and knead it several times.

Form the dough into a cylinder with a 4cm diameter or press it into a 4cmx4cm biscuit mold.

Freeze the dough for 1 hour to firm it up.

Brush the surface with egg white and roll it in sugar.

Slice the dough into 1cm thick pieces and place them on a baking sheet lined with Teflon paper.

Bake at 170°C for 15-17 minutes. Adjust time and temperature based on your oven.

Let the cookies cool on the baking sheet for 5 minutes, then transfer to a cooling rack.