I have messed around with a cauliflower mash recipe (all cauliflower, no potatoes) as well as an apple and parsnip mash recipe with some success.
However, for Christmas dinner last year, I decided to try my hand at my own recipe involving cauliflower, parsnips, and carrots. The result was, in my opinion, incredible. Now, I did have one family member say they were too sweet and waive his wife off when she was asking for the recipe but the rest seemed to really like it. I know myself and my wife and several others REALLY liked them, so I hope you enjoy.