Preheat oven to 375°F. Grease muffin tin or use paper muffin cups.

In a medium bowl with an electric mixer, cream butter and sugar. Add egg. Mix in bananas and milk.

In another mixing bowl, mix flour, baking powder and cinnamon.

Carefully fold in blueberries. If you are using frozen blueberries, fold them while they are still frozen or they will turn the batter purple. Dried blueberries do not need to be reconstituted before they are added.

Fold banana mixture into blueberry mixture carefully, only until the batter is moist. Do not overmix.

Spoon batter into muffin cups, filling cups to the top. Bake for 15-20 minutes, or until muffins are golden brown

Let cool for 5 minutes in the tins, then transfer to a cooling rack.