Preheat your oven to 350°F (175°C). Lightly grease a 9×5-inch loaf pan or line it with parchment paper.
In a small bowl, stir together the flaxseed and water. Set aside to thicken.
In a large mixing bowl, combine the mashed bananas, vegetable oil, granulated sugar, almond milk, and flaxseed mixture. Stir until well combined.
Gradually add the all-purpose flour, baking soda, salt, and nutmeg to the wet ingredients, stirring until just combined. Be careful not to overmix; a few lumps are okay.
Fold in the chopped walnuts and chocolate chips.
Pour the batter into the prepared loaf pan, spreading it out evenly. Tops with more chocolate chips and walnuts.
Bake in the preheated oven for 50-60 minutes, or until a toothpick inserted into the center comes out clean. If the top starts to brown too quickly, you can cover it loosely with aluminum foil for the last 10-15 minutes of baking.
Allow the banana walnut bread to cool in the pan for about 10 minutes, then transfer it to a wire rack to cool completely.