Pre-heat your oven to 160 degrees on bake. Grease and line a 20cm x 30cm slice pan with baking paper, allowing the long edges to overhang.
Place butter and chocolate in a medium saucepan over low heat. Cook, stirring occasionally until melted and smooth. Cool for 5 minutes.
Place eggs and sugar in a large bowl. Whisk until well combined. Sieve flour and cocoa over the egg mixture and gently fold to combine, Gradually pour in chocolate mixture, stirring to combine.
Pour mixture into prepared pan and scatter top with raspberries. Bake for 35-40 mins or until just cooked through. Set aside to cool completely. Cut into 12 pieces to serve.