- Preheat oven to 180C.
- Wash the mandarins and add them whole to a small saucepan. Cover with water and bring to the boil. Gently simmer for 30 minutes, then drain and cool slightly.
- Cut mandarins in half and puree in a food processor.
- Add the melted butter, oil, eggs and sugar to the mandarin puree and process until combined.
- Sift in the flour and baking powder and pulse until just combined.
- Pour the batter into a greased and lined 20cm cake tin and bake in the oven for 50 minutes or until a skewer comes out clean.
- Allow to cool in the tin for 15 minutes then turn out onto a rack.
Once cake has cooked, dust with icing sugar and scatter extra mandarin segments on top to garnish.