Preheat the oven to 350°F (176°C) and line a baking sheet with parchment paper
In a medium bowl whisk the 1 cup oats, 1 cup flour, ¼ cup cacao powder, 1 teaspoon baking soda, 1 teaspoon baking powder, 1 teaspoon cinnamon, and ½ teaspoon salt until well combined.
In a large mixing bowl, beat the banana and ¾ cup sugar until smooth and creamy.
Add the 3 tablespoon coconut oil and 1 tablespoon vanilla and whip until light and creamy.
Slowly add the flour mixture and blend until just combined.
Stir in the 2 cups chocolate chips and ½ cup chopped walnuts until fully incorporated in the cookie dough and drop by tablespoons on the baking sheet.
Press one walnut in the center of each cookie (optional). Bake for 10 to 12 minutes and cool on a wire cooling rack.
Store in an airtight container for up to four days or freeze for up to two months.