Preheat the oven to 180°C conventional or 160ºC fan-forced.
Line a 12 hole muffin tray with paper cases. Sift the dry ingredients into a large bowl, then add the sugars and stir in. Add the egg, Meadow Fresh Milk, Simply Pure Canola Oil and vanilla then beat with a mixer until combined. Scrape the sides of the bowl then add the boiling water and mix until just combined (the batter will be runny). Pour the batter into a measuring cup (it’s easier and cleaner than using a spoon) and pour evenly into each paper case until ¾ filled (don’t over fill or the mixture will overflow).
Place in the oven and bake for 20-22 minutes or until a tester inserted in the centre comes out clean.
Mix icing sugar with hot water. Add Tararua Butter and beat until light and fluffy. Pipe or spread onto muffins. Freeze any left-over icing.