Preheat oven to 180C. Wash the mandarins and add them whole to a small saucepan. Cover them with a little water and bring to the boil. Gently simmer for 30 minutes and then drain and allow to cool a little.
Pop the whole mandarins in a food processor and wizz them up.
Add the butter, oil, eggs and sugar to the mandarin puree and process to combine (make sure the mandarin mix is cool enough before adding the eggs, otherwise you'll make some scrambled eggs!)
Add the flour and baking powder and process very quickly, until just combined. Don't overmix.
Pour the batter into a greased and lined cake or loaf tin.
Bake in the oven for 40 minutes, it should be very brown on top. Double check by popping a skewer in, it should come out clean.
Allow to cool in the tin for 15 minutes then turn out onto a rack.
Drizzle with an orange glaze or dust with icing sugar.
4 tablespoon mandarin juice
2 tablespoon sugar
Over low-medium heat, whisk sugar and mandarin juice in a small saucepan. Continue whisking until sugar has dissolved and mixture has thickened. Pour it over your cooled cake. Voila!