Preheat oven to 180°c. Line a 27x20cm baking pan with baking paper.
Place 200g of chopped chocolate in a medium microwave-safe bowl. Add butter and microwave in 30 second intervals, stirring in between, until melted.
Add caster sugar, eggs, and vanilla to bowl and mix well to combine. Add flour and cocoa and stir until just combined. Fold in 150g chopped chocolate and pour batter into prepared pan. Sprinkle with raspberries and bake for 35 minutes. Melt remaining chocolate and drizzle on top to serve.
Tips
Brownie will still be molten inside straight out of the oven, but will firm up as it cools, while maintaining a fudgy centre