Preheat oven to 175°C. Line a 12-hole muffin tin or a baking dish (measuring about 28 x 22cm) with baking paper.
Melt butter in a small pot on a low heat. Remove from heat and add chocolate. Stir gently until melted then transfer to a large bowl. Add sugar and mix to combine.
Add eggs, one at a time, mixing after each addition.
Fold through brownie mix and salt with a spatula, until just combined. Be careful not to overmix.
Divide mixture between muffin tins or pour into prepared dish, spreading into an even layer.
Bake for 25-30 minutes until a knife inserted into the centre comes out fudgy but not wet.
Allow to cool for 10 minutes before serving.
To serve use a sieve to dust evenly with raspberry powder and cut into 8-10 pieces.