Preheat oven to 180°C (350°F). Line a 12-hole muffin tin with muffin cases or paper baking cups.
Combine all the wet ingredients to a large mixing bowl or jug and mix well.
Into a large mixing bowl sift the flour, baking powder, and baking soda, then add the sugar, cinnamon, nutmeg, and salt. Mix to combine.
Stir in the wet ingredients until the flour is just moistened. Don’t over mix, if you do you will end up with tough muffins.
Fold in the frozen blueberries.
Divide the batter evenly between the muffin cups.
Bake 20 - 25 minutes or until golden brown.
Transfer the muffins to a cake rack and cool slightly.
Serve warm or at room temperature.
Notes
Use a neutral-flavored oil like vegetable oil because if you use a strongly flavored oil it can ruin the taste of the muffins.Use very ripe bananas because bananas are sweeter when they are overripe and they are easy to mash making it easier to mix into the batter.Use brown sugar and not white granulated sugar - brown sugar has molasses added to it and will give the brownies added moisture and flavor.Muffin pan size - Depending on the size of the muffin tin you use, you may or may not get the same quantity of muffins as stated in the recipe. The muffin tin that I used for this recipe has a hole capacity of 100 ml.If you do use a tin that is larger or smaller you will need to increase or decrease the cooking time accordingly.Grease the top of the tin, just in case the batter rises and spills over onto the top when baked. This will stop the muffin tops from sticking to the top of the tin.Filling the muffin cases - You can line the muffin tin with muffin cases, cupcake cases, or just grease and flour the holes. I like to use an ice-cream scoop to fill the cases. The batter is filled level to the top of the pan.Don't overbake - The muffins are ready when you can insert a toothpick in the center and it comes out clean. Test the muffins for doneness after about 20 - 25 minutes of baking.