Preheat the oven to 350F (180C) degrees. Line an 8x8 inch (20x20 cm) pan with parchment paper, leaving an overhang around the edges. Alternatively line with aluminum foil or lightly grease.
Add the butter and finely chopped chocolate to a large glass bowl. Microwave on medium power (not high) for 45 seconds at a time, stirring between each interval. Continue the process until smooth. Alternatively, you can melt them together in a double boiler over low heat.
Once smooth, whisk in the sugar, eggs and vanilla extract.
Sift in the cocoa and flour (if lumpy). Then carefully stir in the cocoa, flour and salt until you no longer see streaks of dry ingredients in the brownie batter.
Using a rubber spatula, very carefully fold about ½ of the raspberries into the batter. Be careful not to pierce or crush the berries.
Pour/spoon the batter into the prepared pan. Gently press the remaining berries into the batter, again, being careful not to break the berries.
Bake in the preheated oven for about 30 minutes or until the top looks set and an inserted toothpick comes out with a few damp crumbs (not gooey batter).
Cool in the pan until the brownies are completely cooled and the pan is no longer warm to the touch.
Lift the brownies out of the pan using the overhang of the parchment paper/aluminum foil. Place brownies on a cutting board and slice using a sharp knife. Wipe off the knife after each slice for cleaner cuts. If you greased the pan (ie didn't line it) cut the brownies in the pan.