Preheat your oven to 175°C (350°F). Line your square pan with parchment paper, leaving overhang for easy removal.
Melt the dark chocolate and butter together using a double boiler or microwave in short bursts, stirring until smooth and glossy. The mixture will smell rich and chocolatey.
In a mixing bowl, whisk the eggs and sugar together until the mixture becomes pale and slightly frothy, about 2-3 minutes. You'll notice it thickening and becoming fluffy.
Stir in the vanilla extract and a pinch of salt into the egg mixture, blending well to incorporate the flavors.
Fold the melted chocolate mixture into the egg mixture gently, using a spatula, until well combined and shiny.
Sift the cocoa powder into the batter and gently fold it in, just until you see no streaks, creating a rich, chocolatey batter.
Pour the batter into your prepared pan, spreading it evenly with a spatula so it looks smooth and shiny on top.
Bake the brownies in the preheated oven for 20-25 minutes. The edges will be firm and slightly pulling away from the pan, while the center remains a little jiggly.
Remove the pan from the oven and let the brownies cool slightly in the pan, allowing the texture to set and develop a fudgy interior.
Lift the brownies out using the parchment overhang, then cut into squares with a sharp knife. The surface will be slightly cracked, with a moist, dense crumb inside.
Serve your rich, chocolatey mummy brownies warm or at room temperature, enjoying the deep cocoa flavor and fudgy texture with a nostalgic feel.
