For the single upside down cake:
1. Grease your cake pan and preheat oven to 350F.
2. Mix together 3/4 cup brown sugar and 6 tablespoons melted butter. Spread evenly over the bottom of the pan.
3. Arrange banana slices (from one sliced banana) on top of sugar mixture.
4. In a separate bowl, mix together 2 1/4 cups flour, 1 1/2 tablespoons baking powder and 1 1/2 cups sugar.
5. Add 1 cup of mashed bananas, 3/4 cup buttermilk, 1/2 cup shortening, 1 teaspoon ground cinnamon and 1 teaspoon vanilla. Beat on low until combined .
6. Beat in two eggs until combined.
7. Pour over bananas and bake about 40 minutes or until a toothpick comes out clean.
8. Cool cake in pan for 10 minutes before inverting onto a serving dish.
For the layer cake:
1. Bake two of the above cakes. Cool and stack with the "upside down" banana parts touching to form the filling layer.
2. Frost with peanut butter frosting ( Beat 1 stick softened butter and 1 cup peanut butter. Add 1 teaspoon vanilla and two cups powdered sugar. Beat until smooth, adding up to 3 tablespoons of milk to smooth the frosting out.)
3. Optional: Top with milk chocolate chips and peanut butter chips.