What can I make out of cauliflower mash?

If you puree it until it's thinner (add a bit of water) and add shredded cheese, it becomes a cheese sauce - depending on the cheese it could be "alfredo" or perfect for macaroni and cheese. I do this for my daughter all the time and freeze it in ice cube trays to just take out a few and mix with cooked pasta or vegetable noodles.

You can use it to top a shepherd's pie - even just one mini in a ramekin.

You can make it into a patty (may need egg/breadcrumb) and pan fry.

You can turn it into a baked "potato" soup or some other cauliflower soup.

i would add olive oil, salt and low fat ricotta and call it a fake mashed potatoes. use it as a side.
you can make a stew: saute chopped onion, add cauliflower small pieces, cubed tomatoes, add more tomato juice and water. when cooked, add salt, pepper and chopped fresh dill.
if you want the version with meat, add chicken pieces when you saute the onion, all the other steps remain the same.

my favorite(if you don't mash it up), bake with a bit of oil pepper and salt, I like mine still a bit crunchy and then at the very end put some Franks hot sauce on it, toss with more pepper.