I actually use banana and apple sauce as substitute often.. adds a little flavour... not sure about adding avocado or black beans though... guess it depends on what you're making! If any of you have tried it, please comment! I'd love to get feedback!
Amazing Chocolate Cake. No flour, no sugar. My friend made it the other night and I fell in love. She used white beans (great northern), coconut oil (not butter), and just honey for sweetening (instead of the other options it provides). Also, for the frosting she sweetened with just honey, but did use butter since coconut oil would separate in a frosting.