Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a large bowl, combine the whole wheat pastry flour, old-fashioned oats, baking soda, baking powder, salt, and cinnamon. Mix well to ensure even distribution.
In a separate bowl, mash the ripe bananas until smooth, then mix in the maple syrup, melted coconut oil, and vanilla extract until fully combined.
Pour the wet ingredients into the dry ingredients and stir until just combined. Be careful not to overmix.
Fold in the dark chocolate chips and walnuts (if using) until evenly distributed.
Using a tablespoon, drop 2-tablespoon portions of the dough onto the prepared baking sheet, spacing them about 2 inches apart. Flatten each cookie slightly with your palm or a spatula.
Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden.
Remove from the oven and let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.