Heat oven to 160°C fan forced. Grease and line a 20cm baking tin.
In a large pot, boil mandarins for 1 hour, and change the water three times.
Carefully Set cut into four and remove any seeds. In a blender or food processor, blitz until smooth. Set aside to cool.
In a kitchen mixer, add the eggs and sugar and beat on medium speed until light and fluffy. Fold through almond meal, cardamom and baking powder.
Place in oven and bake for 45-50 minutes or until set. Set aside to cool.
To prepare the icing, beat cream cheese, icing sugar, mandarin rind and rose water (if using) for 2-3 minutes or until combined. (Do not overmix or mixture will become runny!)
To serve, top cooled cake with icing and decorate with rose petals, dried fruit and pistachios.