I’m from Denmark and in Denmark there is not much of a tradition for eating peanutbutter, let alone peanutbutter and banana. So of course when I made myself such a thing I took a picture.
While I think the peanut/banana combo might work great in a cake I’m not a fan of it on a piece of bread, however it might improve by toasting the bread. Peanutbutter, while delicious, has quite a “sticking-to-the-back-of-your-palate” taste and texture. Banana also has that slightly “over-creamy” taste… together they therefore become too much. But now when thinking about it, it might work on toast.