Grind oats into flour in a food processor. Transfer it into a large bowl.
Add baking powder, vanilla and salt. Mix everything together.
Prepare a vegan egg by mixing ground flax seeds in 2 1/2 tbsp of water. Leave it to stand for approximately 5 min.
Put medjool dates in a small bowl and pour hot water over them so that they become softer.
Mash 3 bananas (360g) well with a fork so that they become creamy and soft. Put them into a large bowl.
Mash softened medjool dates (discarding the water where they were soaking) with a fork. Add them to the bowl with bananas. Mix together.
Melt coconut oil and cashew butter over low heat and add them to the bowl with bananas and medjool dates.
Add also plant based milk and flax egg to the wet ingredients. Mix together well.
Chop the chocolate into small pieces and chop 2 bananas (240g) into chunks.
Heat the oven to 180 °C.
Pour the dry mixture over the wet one. Mix together so that there are no dry spots left but don't over mix it.
Mix chocolate and banana pieces gently into the batter.
Pour the batter into a greased loaf pan (I used 10 x 29 cm) and even out the surface on top.
Cut the last banana in half lengthwise. Gently push it into the batter so that the cut side is looking up.
Put the loaf into a preheated oven on the middle rack for 50-60 minutes. After 50 min of baking test with a knife if the bread is done. If the knife comes out clean from the center then you can take the bread out of the oven. If the center is still wet put the bread back in the oven for a couple of more minutes. If the top is getting too brown, cover it with aluminium foil.
Leave the bread to cool on the cooling rack for 20 min before turning the baking dish carefully around and take the bread out.
Then leave the bread on the cooling rack for at least an hour before cutting into it.