Preheat the oven to 350°F (175°C). Line the base of an 8 1/2 x 4 1/2- inch loaf pan with parchment paper and lightly grease the sides.
In a large bowl, whisk together the mashed bananas, eggs, Greek yogurt, maple syrup, peanut butter (or almond butter) and vanilla extract, until well combined. (Alternatively, blend the wet ingredients in a blender for an ultra-smooth batter.)
In a medium bowl, whisk together the white flour, whole wheat flour, hemp hearts, baking soda, cinnamon, and salt.
Gradually, stir the dry ingredients into the wet ingredients, until just combined. Do not overmix!
Stir in the melted and cooled coconut oil, until incorporated. Then, fold in your choice of mix-ins, if using: 1/2 cup total of dark chocolate chips or chopped nuts or both.
Pour the batter into the prepared loaf pan. (Optional: Slice a banana lengthwise and place it on top for a decorative touch, or arrange banana slices side by side.)Bake for 50-60 minutes, or until a toothpick inserted into the center comes out clean or with just a few moist crumbs.
Let the bread cool in the pan for at least 10 minutes, then transfer the loaf to a wire rack to cool completely.
Slice into 12 pieces and serve as-is or with a spread of nut butter for an extra satisfying snack or quick breakfast.