In a medium bowl, sift together flour and matcha powder
Using a stand or hand mixer, cream the softened butter until smooth (2-3 minutes)
Slowly add in the confectioners’ sugar and mix until fully combined
Add in the egg yolks and mix well
Carefully add in the flour and matcha mixture and mix until fully combined. This will take a few minutes but keep mixing!
Add in the white chocolate chips and mix together
Turn the dough out onto a lightly floured surface and cut in half to make two portions
Roll each portion into a 1 ½ inch (4cm) by 7 inches (18 cm) long cylinder. Wrap them tightly in plastic wrap and store them in the fridge for a minimum of 2 hours
Once chilled, preheat your oven to 350 degrees. Using a sharp knife, slice the dough into 1/- inch rounds, and lay 1 inch apart on a parchment-lined baking sheet
Bake cookies in preheated oven for 15 minutes, or until the edges just start to lightly brown
Remove from oven, allow cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to fully cool