Grease and flour 9"x5" loaf pan. Preheat oven to 350°F (180°C).
In a medium sized bowl, stir together all-purpose flour, baking soda, baking powder, salt, ground cinnamon, and ground nutmeg until combined.
In another bowl, beat together egg, sugar, and vegetable oil.
Blend in mashed banana, vanilla, and buttermilk.
Add dry ingredients, walnut, and chocolate chips all at once to banana mixture. Stir until just combined.
Pour batter into prepared pan.
Bake for 55 minutes, or until wooden pick inserted in the center comes out clean. Place an aluminum foil tent over bread after 40 minutes to prevent it from browning too quickly.
Cool in pan for 10 minutes. Remove and cool completely on wire rack.