In a small saucepan, melt the butter over medium heat. Continue cooking, stirring often, until it foams and turns golden brown with a nutty aroma. Remove from heat and let cool for 10 minutes.

In a large mixing bowl, combine the browned butter, brown sugar, and granulated sugar. Mix until smooth.

Add the egg and vanilla extract, and mix until well combined.

In a separate bowl, whisk together the flour, matcha powder, baking soda, and salt.

Gradually add the dry ingredients to the wet mixture, stirring until just combined.

If using, fold in white chocolate chips or chunks.

Cover the dough and chill in the fridge for at least 30 minutes (optional but recommended for better flavor and texture).

Preheat oven to 350°F (175°C). Line a baking sheet with parchment paper.

Scoop dough into 1.5-tablespoon-sized balls and place on the baking sheet, about 2 inches apart.

Bake for 10–12 minutes, or until edges are lightly golden and centers look just set.

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