Put White Chocolate (300 gram) and Butter (75 gram) in a double boiler, allow it to melt and stir occasionally. Then take the bowl out of the pot and cool off the chocolate for 10 minutes.
Add Egg (3), Vanilla Extract (2 teaspoon), Caster Sugar (1/2 cup) in a mixing bowl and whisk everything together. Then add chocolate mixture and whisk that together. Fold in Self-Rising Flour (1 1/3 cup). Next add White Chocolate Chips (1 cup) and Macadamia Nuts (1/2 cup) and stir those through.
Grease a slice pan and line with some non-stick baking paper. Pour the batter into the pan, spread it so it's even. Preheat the oven to 190 degrees C (375 degrees F) and cook for 20 to 25 minutes or until the top has just set. Leave it in the tin for at least 30 minutes to cool.
Remove it from the pan and dust with some icing sugar. Slice them up.