i've heard of those, but never actually tried them! my brother swears by them (he's a crossfit type, so for him it's about protein, or something, idk). i've baked chocolate cakes with shredded red beets and (different recipe) shredded zucchini, but those weren't flourless. the shredded veg adds a lot of moisture, which i can only recommend. the beets one was so heavy on the cocoa and chocolate the earthy beet flavour was completely masked (which is a nice way to say the cake did not in fact taste like dirt). i'll try to see if i can find the recipe, i don't know if i saved it...

this is the recipe i use for the flourless chocolate/banana cake/brownies, except i omit the cinnamon: https://eatlivepaleo.com/2011/12/26/flourless-choc-cinnamon-banana-cake/