Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a small bowl, whisk together the flour, matcha powder, baking soda, and salt until well combined. Set aside.
In a large bowl, cream the softened butter, brown sugar, and granulated sugar together using a hand mixer or stand mixer until fluffy and light in color.
Beat in the egg and vanilla extract until thoroughly mixed.
Gradually add the dry ingredient mixture to the wet ingredients, mixing on low speed until just combined.
Fold in the white chocolate chips and chopped macadamia nuts (if using) with a spatula until evenly distributed.
Scoop tablespoon-sized portions of dough and place them on the prepared baking sheet, spacing them about 2 inches apart.
Bake for 10-12 minutes, or until the edges are golden but the centers are still soft.
Remove from the oven and allow the cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.