Preheat the oven to 350°F (177°C) and line a 9x9-inch baking pan with parchment paper.

In a large mixing bowl, whisk together melted butter and sugar until combined. Add eggs and matcha powder, mixing until smooth.

Incorporate vanilla extract and milk into the batter, blending until combined. Then add mochiko and sea salt, stirring until uniform.

Pour the batter into the prepared pan and spread evenly. Bake for 40-50 minutes, checking with a toothpick for doneness.

Allow the brownies to cool in the pan for about 30 minutes, then lift them out using the parchment paper.

In a microwave-safe bowl, combine white chocolate chips and heavy cream. Heat in 30-second intervals until melted, stirring in between.

Mix in additional matcha powder to the ganache, then pour it over the cooled brownies, spreading it evenly.

Chill the brownies in the fridge for about 45 minutes until the ganache sets, then slice into 9 squares.