Preheat your oven to 350°F (175°C). Line a 9-inch metal square pan with parchment, letting it overhang two sides for easy lift-out. Lightly grease the pan, especially the corners, to prevent sticking and ensure clean brownie edges.

In a medium saucepan over low heat, melt the chopped chocolate and butter together, stirring constantly until smooth and glossy. Remove from heat and allow to cool for 5 minutes. This prevents scrambled eggs later and supports a shiny top crust.

In a large bowl, whisk together both sugars and the eggs for about 1 minute until pale and thickened. The sugar should mostly dissolve, which adds to the bar’s shiny surface and extra chew. Whisk in the vanilla extract.

Slowly pour the slightly cooled chocolate-butter mixture into the egg-sugar mixture, whisking constantly until evenly combined. Scrape the sides and bottom of the bowl with a spatula to catch any streaks, ensuring a uniform thick batter.

Sift the flour and salt directly over the bowl. Use a spatula to fold until just combined, stop as soon as no floury streaks remain. Overmixing will steal your chewiness and create a tough texture, so watch for a glossy, cohesive batter.

Gently add the raspberries, folding only enough to disperse them evenly without smashing. Take care not to overwork or bruise the fruit. The batter should look streaked with bright bits of fresh berry, not pink and watery.

Scrape batter into the prepared pan and level the top. Bake on the middle rack for 26-30 minutes. The center should feel set but slightly soft, with a toothpick coming out with a few moist crumbs (not raw batter). Do not overbake.

Let brownies cool fully in the pan on a wire rack, at least 2 hours. For perfectly neat slices, chill in the fridge for 30 minutes before lifting out and cutting with a sharp knife wiped clean between cuts.