Preheat oven to 170°C fan bake.
In a large bowl melt butter in the microwave in 30 second bursts.
Add sugar and orange zest & juice, stir again and add the eggs.
Sift in the flour and baking powder. Fold everything together and whisk out any lumps. Stir in ½ cup chocolate chips.
Pour mixture into a lined slice tin then scatter over the remaining chocolate chips.
Bake for 22 minutes until blondie feels firm on the surface.
Allow to cool before cutting into squares. Dust with icing sugar and serve.
