Preheat your oven to 350°F (175°C).
Grease your 9x13 inch baking dish with a little butter or non-stick spray.
In a mixing bowl, combine the mashed bananas and evaporated milk. Stir until well blended.
Pour the banana and milk mixture into the prepared baking dish, spreading it evenly. Drizzle caramel sauce over it, and sprinkle chopped pecans on top.
Sprinkle the cinnamon swirl cake mix evenly over the banana and caramel layers without stirring.
Scatter the thinly sliced butter evenly over the cake mix layer.
Bake for 40-45 minutes, or until the top is golden brown and a toothpick comes out clean.
Allow to cool slightly before serving.
