Preheat oven to 175°C. Grease a 9-x-13-inch pan and line with parchment paper so that it hangs over the sides of the pan.
Over a pot of barely simmering water melt butter for 1 minute, then add chocolate and stir gently until melted. Remove chocolate from heat to cool for 5 minutes.
Whip eggs with sugars and vanilla using electric beaters until thick and frothy. By hand, stir in melted chocolate.
In a separate bowl, stir flour, baking powder and salt, then gently stir into chocolate mixture.
Stir in Skor bits and spoon batter into prepared pan.
Bake for 30 to 35 minutes, until a rich golden colour. Cool to room temperature before removing from pan.
For a fancier treat, melt white chocolate and dip each square halfway and chill to set.