Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper or a Silpat.
Peel the 4 bananas and lay them flat on the prepared baking sheet. Evenly drizzle the 2 tablespoons honey over the bananas and evenly sprinkle the 1/2 teaspoon cinnamon on top.
Roast the bananas at 400°F for 20–25 minutes, until the tops are very golden brown and caramelized. Remove from the oven and let cool about 5 minutes. Once cool enough to handle, mash the bananas and set aside. Reduce oven temperature to 350°F (175°C).
Spray a 9x5-inch loaf pan thoroughly with nonstick spray.
In a small bowl, whisk together 1 1/4 cups white whole wheat flour (or whole wheat pastry flour), 1/2 cup all-purpose flour, 1 teaspoon baking soda, and 1/2 teaspoon salt. Set the dry mixture aside.
In a large bowl, whisk the 2 eggs and 1/2 cup loosely packed brown sugar until smooth.
Measure 1/2 cup canned coconut milk and 1/2 cup coconut oil (use coconut oil melted). If your coconut oil is solid, melt it before measuring. Add the coconut milk and melted coconut oil to the egg and sugar mixture and whisk until combined.
Stir the mashed bananas and 1 teaspoon vanilla extract into the wet mixture until mixed.
Add the dry ingredients to the wet ingredients gradually and stir just until combined; do not overmix.
Fold in 4 ounces chopped dark chocolate and 1/2 cup toasted coconut flakes (if using).
Pour the batter into the prepared loaf pan and smooth the top. Sprinkle the 2 tablespoons unsweetened coconut flakes over the top (if using).
Place the loaf pan on a baking sheet and bake at 350°F for 50–60 minutes, or until the center is set. If the top begins to brown too much, tent the loaf with aluminum foil.
Remove the loaf from the oven and let it cool in the pan for at least 30 minutes before slicing. Store the bread covered for 3–5 days.