Preheat your oven to 180 °C (356 °F) (170 °C (338 °F) fan-assisted) and measure out your ingredients.
Break up 120 g dark chocolate into a microwavable bowl with 100 g unsalted butter.
Heat the butter and chocolate for 30 seconds in the microwave, and mix.
Return the bowl to the microwave for 20-second intervals, mixing each time. Repeat until the chocolate and butter are completely melted and combined.
Add 100 g caster sugar and 50 g light brown sugar while it's still hot, and whisk until smooth. Leave to cool for 5 mins.
While you're waiting for the mixture to cool, line your baking tin with baking paper. The baking parchment should be bigger than the tin, coming over the edges for easy removal at the end.
In a separate bowl add 50 g all-purpose flour, 2 tbsp matcha powder and 1 pinch salt. Mix them together and set aside for now.
By now, the chocolate should have slightly cooled. Add 2 medium egg(s) to the chocolate mixture one by one, whisking between each addition.
Add 1 tsp vanilla essence and whisk one more time.
Sift your dry ingredients into the wet ingredients and then fold them in using a spatula.
Once well incorporated, pour the mixture into the baking tin. It should be a thick batter.
Bake on the middle shelf for around 23-25 mins and test it by piercing the middle with a toothpick, it should come out with moist crumbs. If it's underbaked, return to the oven and repeat the pierce test every 2-3 minutes until it's done.
Remove from the oven and leave to cool for a few minutes before transferring it to a wire rack (keep it in the baking parchment to prevent breakage). Once cooled, cut into 9 or 12 pieces and dust them with 1 tsp of matcha powder.
Enjoy!