Method

1. Preheat oven to 180C. Line a 12-hole 1/3-cup (80ml) muffin pan with paper cases. Place the combined flour, sugar and bicarbonate of soda in a large bowl. Add the raspberries and rhubarb and toss to combine.
2. Whisk banana, oil, egg and milk in a bowl. Stir into the flour mixture until just combined. Spoon into paper cases. Bake for 20-25 mins or until a skewer inserted into the centres comes out clean. Transfer to a wire rack.
3. To make the icing, sift the icing sugar into a small bowl. Stir in enough boiling water to create a smooth, runny paste. Stir in a little food colouring. Drizzle over the muffins.