Preheat your oven to 350°F (175°C) and grease a loaf pan.
In a mixing bowl, mash the ripe bananas with a fork until smooth.
Add the melted coconut oil to the mashed bananas and mix well.
Stir in the brown sugar and vanilla extract until combined.
Sprinkle the baking soda, salt, and cinnamon over the mixture and mix.
Add the flour gradually, mixing until just combined.
If using, fold in the walnuts and plant-based milk for extra moisture.
Pour the batter into the prepared loaf pan and smooth the top.
Bake in the preheated oven for 50-60 minutes, or until a toothpick comes out clean.
Let the bread cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.