Preheat the oven to 350F.
In a baking dish, place the entire head of cauliflower and cover with half of the fat, salt, and water. Bake for 1 1/2 hours.
In a large pot, cook the onion and garlic in the remaining fat until tender.
Chop the cauliflower and add to the pot with the broth.
Simmer 10 minutes, then puree and serve.