Preheat the oven to 350 degrees F. Spray a Bundt pan with nonstick cooking spray.
Mix the granulated sugar and cinnamon in a small bowl and set aside.
In a small saucepan, melt the brown sugar with the butter over low heat. Break open the crescent roll packages and separate the triangles of dough. Brush each triangle with sweetened condensed milk and top with 2 banana slices and 1 teaspoon chocolate chips; fold the edges of the triangle together and seal. Repeat with remaining dough and filling. Sprinkle each with 1/4 teaspoon of the cinnamon sugar.
Put half of the walnuts in the Bundt pan and top with half of the dough packets. Pour half of the brown sugar-butter mixture over the dough and sprinkle with 2 teaspoons of the cinnamon sugar. Repeat with the remaining ingredients. Bake until puffed, golden brown, and firm to the touch. Bake for 1 hour. Remove the pan from the oven, transfer it to a rack and allow it to cool for 15 minutes. Put a platter on top of the Bundt pan and invert. Slice and serve warm.