If your kids think they don't like cauliflower, let them try it roasted to bring out the nutty sweetness. Or call it "Caramelized Cauliflower Bisque" and see if they like the sound of it.
Heat the oven to 450°F.
Cut the cauliflower into small florets and, on a large foil-lined rimmed baking sheet, toss them with the garlic, onion, oil, and 1 teaspoon of salt. Roast 25-30 minutes, flipping the florets halfway through, until they are golden and starting to brown.
Reserve a few small florets for garnish, if you like, then add the rest of the cauliflower along with the onions and garlic to a large pot with the broth and water and bring to a boil over high heat. Lower the heat, then simmer the soup, partially covered, for 30 minutes, or until the cauliflower is very tender.
In a blender in batches, or with a hand blender, puree the soup until smooth.
Stir in the half and half, add black pepper and more salt to taste, and serve, garnished with the reserved florets and snipped chives.