Preheat your oven to 350°F (175°C). Grease an 8-inch square baking pan, and optionally line it with parchment paper for easier removal.
In a mixing bowl, combine flour and salt, then set aside.
In a heatproof bowl, combine chopped chocolate and butter. Place this bowl over a saucepan with simmering water, stirring until melted and smooth. Remove from heat and let it cool slightly.
In a separate bowl, use an electric mixer to beat sugar and eggs together until the mixture is light, thick, and fluffy, about 5 minutes. Add vanilla extract, then gradually pour in the melted chocolate mixture while continuing to mix at high speed.
Gently fold in the flour mixture on low speed until just combined. Transfer the brownie batter to the prepared baking pan and spread it evenly.
Bake in the preheated oven for approximately 30 minutes, or until a toothpick inserted in the center comes out mostly clean. Allow the brownies to cool on a wire rack for 15 minutes.
After cooling, gently press down the edges with a spatula, then let them cool completely at room temperature for 20 to 30 minutes before cutting into 9 squares.
