01 - Preheat oven to 350°F. Line an 8-inch square baking pan with parchment paper, leaving an overhang for easy removal.
02 - In a medium bowl, whisk together flour, granulated sugar, brown sugar, baking powder, salt, and matcha powder until evenly combined.
03 - In a large bowl, whisk together melted butter, egg, vanilla extract, and pumpkin purée until the mixture is smooth.
04 - Add the dry ingredients to the wet mixture. Stir until just combined. Avoid overmixing to retain a chewy texture.
05 - Gently fold in white chocolate chips and, if desired, ground cinnamon to the batter.
06 - Spread the batter evenly into the prepared pan. Sprinkle extra white chocolate chips on top if desired.
07 - Bake for 22 to 25 minutes until the edges are set and a toothpick inserted in the center comes out with a few moist crumbs. Do not overbake for a soft, fudgy texture.
08 - Allow to cool completely in the pan before lifting out using the parchment overhang and slicing into squares.