Creamy Cauliflower and Fennel Soup
3 tablespoons unsalted butter, plus more for serving (or 2 T Olive Oil)
1/2 large yellow onion, thinly sliced
1 small bulb fennel, halved and thinly sliced (okay to include the core)
1/2 large cauliflower, in florets (about 3 cups or 3/4 pound after trimming)
4 sprigs fresh thyme
5 cups chicken or vegetable broth (if canned, use equal parts broth and water)
1/4 teaspoon crushed fennel seed
Kosher or sea salt and freshly ground black pepper
Freshly grated Parmigiano Reggiano cheese
Melt the butter in a large pot over moderate heat. Add the onion and saute until softened and just starting to color, 5 to 10 minutes. Add the fennel, cauliflower and thyme sprigs and stir to coat with the butter. Add the broth and bring to a simmer. Cover and adjust the heat to maintain a gentle simmer. Cook until the vegetables are tender, about 20 minutes. Remove the thyme sprigs.
With a slotted spoon, transfer the vegetables to a blender or food processor and blend until smooth, adding just enough of the cooking liquid to make a puree. Return to a clean pot and stir in the remaining cooking liquid, adding just enough to make soup of a consistency that you like. You may not need it all. Stir in the fennel seed and season to taste with salt and pepper.
Reheat the soup. Divide among soup bowls. Garnish each portion with a sliver of butter and a sprinkle of cheese.