Mix Wet Ingredients. First, add the ripe banana to a medium bowl and mash it with a fork. Next, add sugar, vanilla extract, melted coconut oil, and the egg. Whisk until combined.
Mix in Dry Ingredients. Add the almond flour, cocoa powder, baking soda, cinnamon (optional), and salt to the same bowl with the wet ingredients. Use a spatula and mix everything until combined.
Fold in Chocolate & Nuts. Add chocolate chips and chopped walnuts (if using), and fold everything together until combined.
Chill the Dough. Chill the dough in the refrigerator for about 30 minutes to 1 hour. This will help the cookies to firm up before they bake.
Bake. Preheat the oven to 375 °F (190 C) and line a baking sheet with parchment paper. Remove the cookie dough from the refrigerator and begin scooping dough in 1 ½ Tbsp scoops onto prepared baking sheets. Space cookies 2 inches apart to account for spreading. Bake cookies on a center rack for 12-15 minutes or until edges begin to turn golden brown.
Cool & Enjoy. Remove cookies from the oven and sprinkle with a pinch of sea salt or Maldon salt while still warm for extra flavor contrast and texture. Let the cookies cool for 10 minutes on the tray before enjoying!
Notes
Substitute the egg for 1 flax egg, which is 1 tbsp flaxseed and 2 tbsp water.