Preheat your oven to 350°F (175°C). This ensures that your brownies bake evenly.
Line an 8x8 inch baking pan with parchment paper, allowing some overhang for easy removal later. Grease lightly with butter or cooking spray.
In a double boiler or a microwave-safe bowl, combine the chopped dark chocolate, milk chocolate, and butter. Melt them together, stirring until smooth and glossy. Allow to cool slightly.
In a large mixing bowl, whisk together the light brown sugar and eggs until the mixture is smooth and slightly thickened. This usually takes about 2-3 minutes of vigorous whisking.
Once the chocolate mixture has cooled slightly, add it to the sugar and egg mixture, stirring until combined. In another bowl, whisk together the flour, cocoa powder, and fine sea salt. Gradually add the dry ingredients to the wet mixture, stirring until just combined.
Gently fold in the fresh raspberries, being careful not to crush them. You want to keep those lovely chunks intact for bursts of flavor.
Pour the brownie batter into the prepared pan, spreading it evenly. Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.
Once baked, remove from the oven and immediately sprinkle the large flake sea salt on top. Allow the brownies to cool in the pan for about 10 minutes, then lift them out using the parchment overhang. Transfer to a wire rack to cool completely before slicing.