01 - Line a baking sheet with parchment paper or a silicone mat to create a non-stick surface for the chocolate bark.
02 - Melt the white chocolate in a heatproof bowl set over a pot of gently simmering water (double boiler method), stirring continuously until smooth and glossy. Alternatively, microwave in 20-second bursts, stirring between each interval, until fully melted.
03 - Remove the chocolate from heat source and transfer 2 tablespoons of the melted white chocolate to a separate small bowl. Set aside for marbling.
04 - Sift the matcha powder into the remaining larger portion of melted chocolate to prevent lumps. Mix thoroughly with a spatula until the chocolate is evenly colored and no streaks remain.
05 - Pour the matcha-infused chocolate onto the prepared baking sheet. Using an offset spatula, spread into an even layer approximately 1/4-inch thick across the surface.
06 - Drizzle the reserved plain white chocolate over the matcha layer in a zigzag pattern. Use a toothpick or skewer to drag through both chocolates, creating a decorative marbled pattern.
07 - Immediately sprinkle toasted black sesame seeds and white sesame seeds evenly over the entire surface while chocolate remains fluid. Finish with a pinch of flaky sea salt for depth of flavor.
08 - Transfer the baking sheet to the refrigerator and chill for 30 minutes or until the chocolate is completely firm and set to the touch.
09 - Break the hardened bark into irregular pieces by hand. Store in an airtight container at cool room temperature for up to one week.