Directions
Reserve one-quarter of the cauliflower florets and cut them into small, bite-sized pieces.
In a large saucepan, combine the remaining three-quarters of the cauliflower, 3 cups (720 ml) of the chicken stock, 1½ teaspoons of salt, and the pepper.
Cover, bring to a boil over medium-high heat, then reduce heat to medium and steam until the cauliflower is fork-tender, about 10 minutes.
While the cauliflower steams, heat the oil in a large stockpot or Dutch oven over medium heat.
Add the onion, shallot, garlic, celery, leek, thyme, and the remaining ½ teaspoon of salt.
Sauté for about 7 minutes, until the vegetables are tender and fragrant.
Carefully transfer the steamed cauliflower and its cooking liquid to a high-powered blender.
Add half of the sautéed vegetables and the fish sauce.
Blend until the mixture is completely smooth and creamy.
Return the stockpot with the remaining vegetables to the stove.
Add the remaining 1 cup (240 ml) of chicken stock, using a spatula to scrape up any flavorful browned bits from the bottom of the pot.
Stir in the reserved bite-sized cauliflower florets, the canned clams with their juices, and the additional clam juice.
Bring the mixture to a boil over medium-high heat.
Pour the creamy cauliflower purée from the blender into the stockpot. Return to a boil, then reduce the heat to medium-low.
Simmer for about 30 minutes, stirring occasionally, until the cauliflower florets are tender and the flavors have melded together.