1
Preheat oven to 175°C. Grease + line 20 cm baking tin.
2
Melt butter + chocolate together using bain-marie, ensuring bottom of bowl does not touch water.
3
Remove from heat, stir in sugar + salt until dissolved. Use wooden spatula instead of whisk to avoid incorporating air, keeping brownie dense. This step also cools mixture.
4
Ensure mixture is warm, not hot. Add eggs one at a time, whisking between each addition until batter is completely homogenous + glossy.
5
Sift flour + cacao powder into batter. Fold gently with spatula until just combined, taking care not to overwork it.
6
Pour into tin, tap firmly to remove air bubbles, + finish with extra flaky salt. Bake for 22 minutes until top is set + skewer comes out slightly moist!