Prepare the Dry Ingredients: In a medium mixing bowl, whisk together 300 g of all-purpose flour and ¼ teaspoon of salt until well combined. Set this mixture aside while you work on the wet ingredients.

Cream the Butter: Using an electric hand mixer, beat 230 g of softened unsalted butter in a large bowl until creamy, about 2–3 minutes.

Add Sugar and Egg Yolk: Gradually add 100 g of granulated sugar to the creamy butter, then add 1 egg yolk and 1 teaspoon of vanilla extract, mixing until combined.

Combine Dry and Wet Ingredients: Incorporate the flour and salt mixture into the butter mixture, mixing gently until just combined.

Divide the Dough: Divide the dough evenly into two halves. Keep one half as the vanilla dough, and to the other half, sift in 20 g of matcha powder.

Shape the Dough: Press each dough half into rectangles, then roll each rectangle out to about ¼ inch thick.

Chill the Dough: Transfer the dough sheets to the refrigerator and chill for at least 1 hour, or until firm.

Stack the Dough Sheets: Peel away one dough sheet and lay it atop the other. Brush one edge with egg white to glue them together.

Chill Again: Chill the stacked dough for an additional 15 minutes.

Cut the Stripes: Cut the stacked dough into ¼ inch wide strips.

Assemble the Layers: Lay one strip flat, brush with egg white, and place another strip on top, alternating colors.

Chill the Completed Blocks: Once assembled, place the blocks of dough back in the refrigerator until firm.

Preheat the Oven: Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

Slice and Arrange the Cookies: Slice each dough block into ¼ inch thick cookies and arrange them on the prepared baking sheet.

Bake and Cool: Bake the cookies for 12-15 minutes, then cool for 5 minutes on the baking sheet before transferring to a wire rack.