Pre heat oven to 190oC.
Take the peeled bananas in a bowl and mash it well with hands to make it a paste.
Add oil, vanilla sugar to it and mix well. Keep a side.
Mix flour, baking powder, baking soda in another bowl with a whisk.
After mixing properly make a dent and pour the banana mixture in the dent.
Fold gently, do not over mix, just mix well so that every thing blends properly and don't beat.
With ¾th of the walnuts added to it, reserve some for sprinkling on the top.
Line the muffin tray with paper liners and spoon the batter in it up to ¾th of it.
It will raise so much so make sure you leave room for it. Top with some walnut sprinkled over it.
Bake for 30 minutes or until the toothpick inserted comes out clean and top turns golden brown.
Mine got baked at around 28 minutes itself, so keep an eye after 25 minutes.