Preheat the oven to 180°C. Place 12 paper muffin cases in a 12-hole muffin tin.
Sift the flour, baking powder and mixed spice into a large bowl. Add the caster sugar and stir to combine.
Mix together the Puhoi Valley Milk, Puhoi Valley Feijoa Yoghurt, egg and oil. Make a well in the centre of the flour and mix in the liquid ingredients. Mix in the chopped feijoas and white chocolate.
Spoon batter into the muffin cases until two-thirds full. Mix together the caster sugar and cinnamon. Top each muffin with a slice of feijoa, if using and sprinkle with cinnamon sugar. Place in the oven and bake for 20-25 minutes.
Remove from the oven and leave to sit for 5 minutes before removing muffins and placing on a wire rack.
Serve warm or cool topped with extra Puhoi Valley Fabulous Feijoa Yoghurt if wished.