Place the chopped semi-sweet chocolate (or chocolate chips) in a heatproof bowl, add the butter, and set the bowl over a pot of gently simmering water. Stir gently until the mixture is fully melted and smooth, then remove from the heat and let it cool slightly for 3-4 minutes.
In a separate bowl, whisk together the eggs, sugar, and brown sugar until fully combined. Slowly drizzle in the melted chocolate-butter mixture, whisking continuously to blend everything smoothly.
Sift in the flour and cocoa powder, then gently fold just until combined. Add the vanilla paste and salt, mixing until the batter is smooth. Pour into a parchment-lined 20×20 cm (8×8 inch) pan and spread into an even layer.
Bake in a preheated oven at 355°F (180°C) for 25–30 minutes, or until a toothpick inserted comes out with moist crumbs. Allow the brownies to cool completely in the pan.
For the ganache, warm the cream in a saucepan just until it begins to simmer. Place the chopped dark chocolate in a heatproof bowl and pour the hot cream over it. Let it sit undisturbed for 5 minutes, then stir gently until smooth and glossy.
Pour the ganache over the cooled brownies and smooth it out evenly with a spatula. Refrigerate for at least 1 hour to allow it to set. Once firm, lift out of the pan, peel away the parchment, and cut into squares.
Notes
Let the Chocolate Ganache Cool: I like to let the melted chocolate mixture sit for a few minutes before adding it to the eggs. If it’s too hot, it could scramble the eggs, so giving it a moment keeps the batter smooth and silky.Go for Moist Crumbs: I always check with a toothpick; it shouldn’t be clean! That’s how you get the fudgy center.Fold Gently: I stop mixing once the flour disappears to keep the texture dense and fudgy.Use a Sharp Knife to Slice: I run a knife under hot water and wipe it clean between cuts for the cleanest squares.