01 - Preheat the oven to 350°F. Line an 8x8 inch baking pan with parchment paper, leaving an overhang for easy removal.
02 - In a heatproof bowl set over simmering water, melt the chocolate and butter together, stirring until smooth. Remove from heat and let cool slightly.
03 - Whisk the granulated sugar and brown sugar into the melted chocolate mixture until fully incorporated.
04 - Add eggs one at a time, whisking thoroughly after each addition. Stir in vanilla extract.
05 - Sift flour, cocoa powder, and fine sea salt into the mixture. Gently fold with a spatula until just combined to avoid overmixing.
06 - Pour batter into the prepared pan and smooth the surface. Evenly sprinkle flaky sea salt on top.
07 - Bake for 28 to 32 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
08 - Allow to cool completely in the pan on a wire rack. Lift brownies out using parchment overhang and cut into 16 squares.