Preheat oven at 200ÂșC.
Prepare and line the muffin tin for 12 muffins.
Mix the egg, vanilla essence and oil with a whisk until combined.
Mix in the sugar and flour and stir with a wooden spoon with as few strokes as possible, just wetting the dry ingredients. Doesn't matter if it looks as though the mixture is not mixed well.
Pour in the blueberries, and stir less than 5 times.
Bake in the oven for 15-20 minutes.