Will it work to use red and purple sweet potatoes n place of white in the autumn vege root gratin? Can yucca be used since it is starchy?

Thanks! I just wanted to ensure I had enough starch for a "rich" consistency.

Yucca would be a wonderful addition.

red and purple sweet potatoes would definitely work! i've never cooked with yucca, but i think it would work just fine.

I think you could! I've made this gratin with acorn squash and carrots in the stead of parsnips and butternut squash and it turned out just fine; think it would take to most root vegetables. Seems like yuca would be a fine fit -- this article is a good resource: https://food52.com/blog/12433-all-about-yuca-and-how-to-put-it-to-good-use.