Preheat oven to 350℉. Prepare a 8x5 inch loaf pan by greasing it with the butter and a little flour.
Rinse a cup of blueberries and sprinkle them with a bit of flour. This will help so that the blueberries won't sink to the bottom.
In a medium bowl mash the bananas with a fork. To this bowl at the oil, milk, vanilla extract, egg, sugar and whisk. Add sugar and whisk.
In another bowl mix together the flour, baking powder and salt. Mix the flour mixture with the wet mixture using a wooden spoon or spatula. Add blueberries and mix so that the blueberries are evenly distributed in the batter.
Pour batter in prepared baking loaf pan and bake for about an hour or until an inserted toothpick comes out clean.
Remove loaf from pan and let cool before slicing into it.
Wrap this bread tightly with plastic wrap or you can store it in an airtight container. It will last on your counter for 3 days, or in the fridge for about one week. I love to microwave my slices of banana bread for 20-30 seconds to let it soften up, especially if it’s been in the fridge.
Freeze the whole loaf or individual slices. It will last in the freezer for 3 to 4 months! Wrap the loaf or the individual slices extremely well with plastic wrap, even if they’re being stored in an airtight container. The bread will give off some moisture which can cause freezer-burn without the plastic wrap. Let it thaw completely at room temperature.