Place butter, sugar, sour cream into a large mixing bowl or stand mixer, beat until well combined. Add, mashed bananas, mixing until well combined. Add flour, baking soda, salt, and crushed Oreos, mixing until well combined. Transfer to prepared baking pan, spreading evenly. Drizzle prepared caramel sauce over top of cake and run a knife through to swirl through. Bake for 35-40 minutes, or until baked through. Remove from oven and prepare icing.