MICHELLE:
Good afternoon. Why can't you just make a brownie recipe. Then take a box of Vanilla pudding mix follow it's directins. Then ladle it over the top the brownie cake. When just about coagulated, then at that moment top it off with sliced bananas. Then just gently press the slices into the pudding while the pudding still soft, this way the slices will not oxidize. Let us all know of your success.
Michelle, good luck & I hope you have an easy time of it next week. Have a nice day young lady.
~Chef Dunask.