Step 1: Preheat your oven to 325°F (165°C) and line an 8×8 inch square baking pan with parchment paper, leaving an overhang on the sides for easy removal.
Step 2: In a heat-proof bowl, combine the melted butter and 1 cup of the chopped white chocolate. Stir until the chocolate is completely melted and the mixture is smooth.
Step 3: In a separate large bowl, whisk the eggs and granulated sugar together vigorously for about 3-5 minutes until the mixture is pale, thick, and doubled in volume.
Step 4: Whisk in the vanilla extract and the butter-chocolate mixture into the egg mixture until well combined.
Step 5: Sift the all-purpose flour, matcha powder, and salt over the wet ingredients. Using a spatula, gently fold the dry ingredients in until no streaks of flour remain.
Step 6: Fold in the remaining 1/2 cup of chopped white chocolate chunks.
Step 7: Pour the batter into the prepared pan and smooth the top with a spatula. Bake for 22-26 minutes, or until the edges are set and a toothpick comes out with a few moist crumbs.
Step 8: Allow the brownies to cool completely in the pan before lifting them out and slicing into 16 squares.