Preheat oven to 350F. Grease and line a 9-inch square baking pan with overhanging parchment paper.
In a medium-sized bowl, sift together the flour, cocoa, baking powder and salt. Set aside.
In a large microwave safe bowl, add 6 ounces of chocolate and the butter. Microwave on 30 second intervals, stirring in between each interval, until the chocolate and butter are melted together and smooth.
Whisk in the sugar and let cool slightly (about 5 minutes).
Whisk in the eggs (one at a time) and vanilla.
Add the dry ingredients to the wet mixture and stir until just combined. Be careful not to over mix. The batter will be very thick.
Gently fold in most of the raspberries and the 2.5 ounces of chopped chocolate or chocolate chips (reserving some for the top).
Use an offset spatula to spread the batter out in the prepared pan. Top with remaining raspberries and chopped chocolate.
Bake for 33-37 minutes, or until a toothpick inserted into the brownies comes out with just a little bit of batter on it.
Let cool on a wire rack before lifting out of the pan and cutting into squares.
Notes
You can use a double boiler on the stovetop to melt the chocolate and butter together if you don't want to use the microwave.
For this recipe, weighted measurements are included to ensure greater accuracy with the ingredients. If you're using cup measurements, be sure to use the spoon and level method for the flour and cocoa. Scooping them out of the bag or container will pack them into your measuring cup and result in too much flour and/or cocoa for the recipe.
Letting the chocolate mixture cool for 5 minutes before adding room temperature eggs will ensure the eggs whisk into the batter easily.
Gently fold in the raspberries. It doesn't matter if some of the raspberries break apart, but you don't want all of them to get mushy in the batter.