Preheat your oven at 180C / 350 F. Grease and dust a loaf tin properly.
If you are bananas are frozen, thaw them for 15-20 minutes at room temperature. Take the chopped bananas in a mixing bowl and mash very well with a spoon or whisk.
Add oil, sugar and vanilla extract to the mashed bananas. Mix well and whisk until the whole mixture turns pale, light and fluffy.
Place a sieve over the bowl containing wet ingredients. Add wheat flour, cocoa powder, salt, baking powder and soda. Sift the dry ingredients over the we ingredients and mix.
Cut and fold the dry ingredients and whip up the batter. Add milk and mix
Throw in the chopped walnuts and mix.
Pout the batter into the prepared loaf tin and tap once or twice. Top with chopped dark chocolate
Bake in the preheated oven for 35-45 minutes or until a tester comes out clean.
Let the cake cool in the tin for 10 minutes.
Remove from the pan and cool for 20 minutes.
Slice and serve as required