Pre-heat your oven to 180°C/ 356°F. Grease a rectangular baking tin with a small amount of vg butter.
Smash your bananas up to form a smooth banana paste. I use a food processor for this (it makes it way easier and quicker).
After your banana paste has formed, place it into a large bowl. Then add the oil, sugar, baking soda, baking powder and flour to the bowl, in that order. Whisk together after each ingredient addition. If you used a food processor to blend the bananas, you could just mix the ingredients in there, whizzing it until combined.
Add the raspberries and 80% of the white chocolate chips (the remaining will be used for the top of the banana bread). Mix until all combined.
Pour the batter into the greased baking tin. Cut your whole banana in half and place on top of the mixture, seed side up. This stage is optional, you can make the banana bread without this (note. this whole banana cannot be overripe otherwise it might make the bread soggy). Bake the banana bread for 50 minutes, or until a knife comes out of the middle clean. If a knife comes out of the middle wet, keep the banana bread in the oven for further minutes, until it is completely cooked. This may be due to your oven temperature/ heat spots. You may want to cover the banana bread with baking paper so that it doesn't brown the outside too much.
Remove from the oven and add the remaining white chocolate to the top of the banana bread, around the sliced banana. Once melted, you can spread the chocolate to even it across the surface. Leave to cool for 10 or so minutes before removing from the tin and serving. Alternatively, leave it to fully cool before you enjoy!