I have NO idea how it would taste, as me and cauliflower are mortal enemies, (yuuck!) but I invented a mashed potato dish that everyone likes. I call it "Baked Potato Casserole". In your case, take the mashed cauliflower, stir in the usual baked potato toppings like sour cream, bacon bits, shredded cheese, butter, salt and pepper to taste.
Put it in a casserole dish while it's still hot, and top with shredded cheese. Place in a preheated 385 deg. oven for 8-10 minutes, or until it turns golden brown. (keep an eye on it. Cheese can burn quickly) Like I said, this is a great "mashed potato" recipe, I don't have a CLUE how it'll taste with cauliflower, and I'll NEVER find out!!! Lol! Good luck...