Preheat the oven to 350°F. Lightly grease a 9×5-inch loaf pan with coconut oil.
In a large bowl, mash the banana well.
Add the remaining wet ingredients (almond milk, melted oil, maple syrup, and vanilla) into the banana and mix until combined.
Stir the dry ingredients (ground flax, coconut sugar, oats, baking soda, baking powder, salt, and flour) into the wet mixture, one by one, in the order listed. Don’t overmix. As soon as all the ingredients are combined, stop.
Lastly add the walnuts (1/2 cup) and chocolate.
Spoon the dough into the loaf pan and spread it evenly. Add the remaining ¼ cup of walnuts to the top of the dough, gently pressing them into the dough.
Bake the loaf, uncovered, for 45 to 50 minutes until lightly golden and firm on top. The top of the loaf should slowly spring back when you press on it.
Allow the loaf pan 20 minutes on a cooling rack to cool completely. Loosen with a knife and remove it from the pan, placing it again onto the cooling rack. It’s hard to wait, I know!
The loaf will keep in the fridge tightly wrapped for 3 to 4 days, or it can be frozen for 4 to 5 weeks.