Preheat the oven to 190°C. Coat the sides and bottoms of 4 mini loaf pans (5 3/4 by 3 1/4 by 2 1/4 inches) with nonstick cooking spray.
Whisk together both flours, the baking powder, baking soda, cinnamon, ginger and salt in a medium bowl. Set aside 1 tablespoon of the dry mixture in a small bowl.
Using a fork, mash 2 1/2 bananas with both sugars in a large bowl until the mixture is mostly smooth with a few small pieces of banana. Add the oil and egg and stir until combined. Stir in the dry ingredients until just combined and then stir in the milk. Toss the chocolate chips with the reserved flour mixture and fold into the batter. Divide the batter among the prepared mini loaf pans. Thinly slice the remaining 1/2 banana and place 4 to 5 slices in an overlapping line down the center of each mini loaf on top of the batter.
Bake until the tops of the loaves are golden and a toothpick inserted into the center comes out clean, 30 to 35 minutes. Cool the breads in the pans for 10 minutes and then turn each pan upside down to release the breads. Cool completely, banana slice side up, on a wire rack.
Cook's Notes: To freeze for later use, wrap each loaf first in plastic wrap and then foil. Take out the frozen loaves the night before using and thaw in the refrigerator.
You can also bake the batter as 1 large loaf in a greased 9-by-5-inch metal loaf pan for 55 to 60 minutes, covering the bread in the last 10 minutes with a piece of foil if it browns too quickly. Cool in the pan 10 minutes and then turn out and cool completely on a wire rack.