Pre heat oven to 200 C. For big topped muffins, line 8 standard size muffin cups with paper liners. Fill the remaining cups with 1 to 2 tablespoons of water to help the muffins bake evenly.

Whisk the flour, sugar, baking powder and salt in a large bowl.

In another bowl, whisk the oil, mashed banana, egg, milk and vanilla until blended.

Add the banana mixture to the bowl with dry ingredients then use a fork to combine. Fold in the blueberries.

Divide the batter between muffin cups. Sprinkle a little sugar on top of each muffin.

Bake muffins 15 to 20 minutes remaining until tops are no longer wet and a toothpick inserted into the middle of a muffin comes out with crumbs, not wet batter.

Transfer to a cooling rack.