If you're impartial to using mayo or cheese, you can definitely substitute avocado for a vegan mayo or cottage cheese. If you're not vegan, of course, you can try with regular mayo and cottage cheese to make this sandwich super creamy and dreamy. Otherwise, if you don't want to use a mayo or a cheese, you can try just using chickpeas on their own and blend them up with a little olive oil or tahini to give it a bit of a creamy hummus-like texture.