Preheat the oven to 350°F. Prepare an 8x8 inch square baking pan with parchment paper, leaving some hanging over the sides to make it easier to remove the brownies from the pan.
Melt butter in a microwave-safe bowl. Add in brown sugar and white sugar and whisk well, until the mixture pulls away cleanly from the sides of the bowl (almost like a paste).
Whisk in the vanilla extract and eggs.
Sift the matcha powder to remove clumps (don’t skip this step!) and whisk it together with the salt and flour. Pour all dry ingredients into the bowl then whisk until just combined - do not over-mix. Stir in the chocolate chips or chopped chocolate.
Pour the batter in the prepared pan, spreading it around in an even layer and bake for 25-35 minutes, or until a toothpick inserted in the middle of the brownies comes out with just a few wet crumbs on it (not completely clean, but not covered in batter).
Sprinkle the tops of the brownies with flaked sea salt if desired. Let cool in the pan completely before slicing.
Video
Notes
Measuring Flour and Matcha: Be sure to properly measure your flour and matcha powder using either a kitchen scale or the scoop and level method. The matcha is very easy to over-measure if you don't weigh it, which can give the brownies too strong of a matcha flavor.Sifting the Matcha: don’t skip this step! Matcha often has lots of clumps in it, which are almost impossible to get out once they are in the brownie batter. Sifting it will help remove the clumps and evenly distribute the powder throughout the batter.Don't over-mix: When you add in the dry ingredients, use a whisk to mix the brownies just until the specks of flour have disappeared, then stop.Baking Time: This will vary depending on your oven. If using a glass baking dish instead of aluminium, the brownies will take longer to bake as well. I recommend checking on the brownies early on so that they don't get over-baked.Storage Instructions: Store un-sliced in the pan, covered tightly with tinfoil for up to 3 days. If they've already been sliced, you can store them at room temperature in an airtight container. Doubling Instructions: To double the recipe, double all ingredients and bake the brownies in a 9x13 pan for 20-30 minutes.