Bring water to a boil in a medium saucepan, add cauliflower florets, and boil until tender, about 15 minutes.
Drain cauliflower and pour into food processor.
In a medium skillet over medium low heat, heat butter, garlic, and rosemary until fragrant. Remove from heat and add to food processor with cauliflower. Pulse until combined.
To food processor, add heavy cream, parmesan, salt, and pepper and pulse until smooth consistency is reached.
For gravy, in a medium saucepan over medium high heat, heat butter, heavy cream, and chicken stock. Bring to a boil, then reduce, cover, and simmer for 12 minutes.
Remove from heat, add xanthan gum and pepper, and whisk together until thick consistency is reached.