I’ll come right out and say with this one that it is waaaaaay easier to just mash up a banana with a fork. However, if you do want it more creamy than chunky, or want to be able to freeze it than simply blend however many bananas you want with a small amount of water or breastmilk/formula until blended.
I also discovered that when I did it this way the bananas are going to turn a bit brown and there’s no way around it. Mashing with a fork on the spot is so easy and is the perfect thing to take on the go! I have taken a banana with me for my son many of times, he loves them!