Heat oven to 350 degrees F. (325 if using a convection oven)
Place the cereal into the bowl of a food processor and pulse until it turns to crumbs. Pour melted butter over the crumbs and pulse to combine.
Reserve approximately 1/2 cup of crumbs and press the remaining crumbs into the bottom of a 13 x 9 inch baking pan. Bake the crust for 8 minutes and remove from oven. Let cool slightly (about 5 minutes).
Meanwhile, melt all but 1/2 cup of the chocolate chips and the sweetened condensed milk together in a heavy saucepan over low heat. Stir occasionally until the mixture is smooth and glossy. Remove from heat and stir in the vanilla extract.
Arrange the sliced bananas across the bottom of the crust. Pour the chocolate mixture over the top of the bananas and spread to cover as much surface area as possible. Combine the remaining 1/2 cup of crumbs, 1/2 cup of chips, and the chopped nuts together and sprinkle over the chocolate filling.
Bake for 20-25 minutes, or until the center is set. Cool in pan before slicing and serving.