Preheat oven to 285 degrees F (140 degrees C).
Add Butter (250 gram) and Dark Chocolate Chips (250 gram) to a bowl. Microwave for 30 seconds, remove and stir, then microwave again for 30 seconds. Let cool.
In a large mixing bowl, add Egg (3) and Brown Sugar (1 cup). Beat together until fluffy. Pour in cooled chocolate mixture and beat until well combined.
Add All-Purpose Flour (1 cup) and the Baking Powder (1/4 teaspoon). Fold together.
Line a 4 centimeter deep pan with baking paper and pour half the brownie batter. Scatter Frozen Raspberries (1 cup) over the brownie mixture. Add White Chocolate Chips (1/2 cup) and then pour over the remaining brownie batter.
Bake for 35 minutes or until firm on top.
Leave in tin for 30 minutes to let the brownies firm up, then slice into pieces and sprinkle with Powdered Confectioners Sugar (to taste).