Preheat your oven to 350°.
Prepare a 12" cast iron skillet or similar with a baking spray or 2 8" round cake pans or a 13x9 pan for easy release.
In the bowl of, a mixer beat the butter, then add in the sugar and mix it until it's light and fluffy.
Add in the eggs one at a time mixing well after each egg is added.
Mix in the banana.
Add in the flour, baking powder, and salt,.
As you begin to blend that in pour in the milk as you're mixing on low to medium speed.
As it combines raise the speed to medium for about 15 seconds so it's all smooth and well blended.
Stir in the blueberries by hand so they don't become a mess and break all into pieces.
Pour the batter into the prepared pan.
Bake at 350° for 30 minutes or until the toothpick comes out clean.
While the cake is cooling mix up the frosting.
Beat the cream cheese and butter until smooth in the bowl of a mixer.
Add in the powdered sugar and heavy cream, start on low until the powdered sugar is combined so it doesn't make a mess, then increase the speed to medium and then to high, it'll whip up smooth and silky.
Spread the frosting over the cooled cake and top with additional blueberries and some basil leaves is desired.