01 - Preheat oven to 350°F. Line an 8-inch square baking pan with parchment paper, allowing overhang for easy removal.
02 - Whisk together flour, baking powder, and salt in a medium bowl until thoroughly blended.
03 - Whisk melted butter, brown sugar, and granulated sugar in a large bowl until combined and glossy.
04 - Add eggs one at a time, whisking well after each addition. Stir in vanilla extract and black sesame paste until fully incorporated.
05 - Fold in dry ingredients using a spatula until just combined. Avoid overmixing to maintain tender texture.
06 - Gently fold in half the toasted black sesame seeds and optional white chocolate chips until evenly distributed.
07 - Spread batter evenly in prepared pan. Sprinkle remaining black sesame seeds across the surface.
08 - Bake for 22-26 minutes until center is just set and toothpick inserted comes out with moist crumbs.
09 - Cool completely in pan before lifting out using parchment overhang. Cut into squares for serving.