Lightly spray a 6-cup loaf pan. In a large mixing bowl, combine the baking mix, 2 teaspoons of pumpkin pie spice, the mashed bananas, egg, and oil. Using a hand mixer, beat the batter for 2 minutes. Remove 1/2 cup of the batter to a small bowl with the brown sugar, 1/2 teaspoon pumpkin pie spice and mix well. Pour the remaining batter into the loaf pan. Pour the brown sugar batter into the loaf pan and swirl with a knife. Make a foil ring and arrange it on the bottom of the slow cooker, then put the loaf pan on top of the foil ring.
Cover slow cooker with 5 paper towels before securing the lid. Cook on low setting until tester comes out clean, about 4 hours. Remove the loaf pan from the cooker and cool on wire rack. When cool, turn the cake out onto a serving platter and serve with the chocolate whipped cream.
For Chocolate Whipped Cream:
Beat the cream with a hand mixer, until it starts to thicken. Add the confectioners' sugar and cocoa powder and continue beating until firm peaks form.