Preheat oven to 180°C. Line a 12-hole, 1/3 cup (80ml) muffin pan with paper cases.
Combine the flour, sugar and cinnamon in a large bowl. Whisk egg, milk, oil and banana in a medium bowl. Add to the flour mixture with the blueberries and stir until just combined (don’t overmix).
Divide the blueberry mixture among the paper cases. Bake for 20-25 mins or until a skewer inserted in the centres comes out clean. Transfer muffins to a wire rack to cool slightly. Dust with icing sugar. Serve the muffins warm or at room temperature.