In a mixing bowl, whisk together the all-purpose flour and salt until well combined.

In a separate bowl, cream the softened unsalted butter until light and fluffy, then gradually add granulated sugar and beat until smooth.

Incorporate the egg yolk and vanilla extract, mixing until fully combined.

Slowly add the flour and salt mixture into the butter mixture, stirring with a spatula until just combined.

Divide the dough into two halves, shape into disks, cover, and refrigerate for 30 minutes.

Sift matcha powder over one half, knead until color is even, shape into a rectangle, and repeat with the other half.

Refrigerate both doughs wrapped in parchment paper for at least one hour.

Place the dough rectangles side by side, brush edges with beaten egg white, and cut into strips.

Layer the strips alternating between matcha and vanilla dough, then press together to form a block.

Wrap the block in plastic wrap and chill for 15-30 minutes, then preheat oven to 350°F.

Slice the block into cookies and bake for 12-15 minutes or until edges are golden.

Cool on a wire rack before serving.