Preheat the oven to 350 degrees F.
Grease a 8x8 baking pan with butter and line with parchment paper. Set aside.
Heat the butter over high heat until it melts. Lower the heat to low. Heat the butter until small brown bits start to appear. Remove from the stove.
Add white chocolate and matcha powder to a small bowl. Pour the brown butter over the top and stir until all the chocolate melts. Let the mixture cool for 2 minutes.
In large bowl, combine granulated sugar, brown sugar, eggs, vanilla extract, and salt. Beat with a hand mixer or stand mixer until thick and creamy (5-10 minutes).
While mixing, stream in your matcha chocolate ganache from step 4. Whisk until a uniform green batter appears.
Lastly, sift your flour into the bowl. Using a spatula, gently fold the flour into the batter using a until a green batter forms.
Spoon into your prepared baking pan.
Bake for 20-30 minutes.
Take out the brownies and slam them on the counter to get rid of some the air. Sprinkle some flaky sea salt over the top and put the brownies back in the oven. Bake for another 10 minutes.
Let cool for 20 minutes before serving.