Preheat oven to 350 F. In a large bowl, cream together the butter and sugars. Beat in banana, eggs, vanilla and milk.
In a medium bowl, mix together the flour, salt, baking powder, and cinnamon. Add the dry ingredients along with the oatmeal to the wet and stir just until combined.
Line a muffin tin with cupcake papers and fill them 2/3 full with batter. Bake at 350 F for 17-18 minutes or until an inserted toothpick comes out clean. Cool completely.
To make the frosting, beat the cream cheese and butter in a mixer until fluffy. Beat in the vanilla, powdered sugar and enough of the cream until spreadable.
Pipe or spread the frosting onto the cupcakes and enjoy!