Preheat your oven to 180°C (350°F). Line your baking pan with parchment paper, leaving an overhang for easy removal.
Chop the dark chocolate into small pieces and melt it in a heatproof bowl set over simmering water, or briefly in the microwave, stirring until smooth. Let it cool slightly to avoid cooking the eggs.
In a mixing bowl, beat the unsalted butter and sugar together until creamy and slightly fluffy, about 2 minutes. This creates a smooth base for the batter.
Add the eggs one at a time, mixing well after each addition, until the mixture is glossy and smooth. Stir in vanilla extract and espresso powder to deepen the flavor.
Gently fold the melted chocolate into the wet mixture, maintaining its glossy texture. The batter should be rich and smooth.
Sift together the flour, baking powder, and a pinch of sea salt. Carefully fold these dry ingredients into the chocolate batter in two additions, just until combined—do not overmix to keep the brownies tender.
Pour the batter into the prepared pan and smooth the top with a spatula. Sprinkle a tiny pinch of sea salt over the surface for contrast and flavor enhancement.
Bake for 25-30 minutes, until the top is cracked and matte, and the edges are set. The center should still be slightly jiggly for that perfect fudgy texture.
Remove from the oven and let cool in the pan on a wire rack for at least 20 minutes. This allows the brownies to set and develop their chewy, fudgy interior.
Using the parchment overhang, lift the brownies out of the pan. Transfer them to a cutting board and slice into squares. Serve slightly warm or at room temperature for maximum gooeyness.
Enjoy your beautifully cracked, fudgy brownies with a sprinkle of sea salt for that perfect salty-sweet finish.
