It's true that cauliflower mash is not as thick as mashed potatoes. This is because it lacks starch. But I find that as long as you drain the florets well, avoid overcooking them, and add plenty of butter, the mash is nice and thick. Another trick is to add 1/4 cup of dry-grated parmesan cheese to the mash itself. Add it to the food processor with the butter, garlic, and salt & pepper.