This recipe is based on a recipe from Epicurious with a few changes I made.
1 medium head of cauliflower (about 2 pounds), cut into small florets
2 tablespoons extra-virgin olive oil, plus more for drizzling
Kosher salt, freshly ground pepper
4 slices pancetta
1 small fennel bulb, chopped
1 small onion, chopped
1 garlic clove, finely chopped
1/3 cup dry white wine or water
6 cups beef broth
3/4 cup heavy cream
2 bay leaves
Preheat oven to 400°F. Toss cauliflower and 2 Tbsp. oil on a baking sheet; season with salt and pepper. Roast, tossing once, until florets are browned all over and tender, 30–35 minutes.
Meanwhile, cut pancetta into 1/2″ pieces. Heat a heavy pot over medium and cook pancetta, stirring occasionally, until browned and crisp. Transfer to paper towels.
Cook fennel, onion, and garlic in drippings in pot, stirring occasionally, until onion and fennel are very soft, 8–10 minutes. Add wine and cook until mostly evaporated, about 5 minutes. Add roasted cauliflower, broth, cream, and bay leaves; season with salt and pepper. Bring to a boil, reduce heat, and simmer until cauliflower is very tender, 20–25 minutes. Pluck out bay leaves; discard. Let mixture cool slightly.
Working in batches, purée cauliflower in a vitamix. Season with salt and pepper.
Just before serving, ladle soup into bowls; top with pancetta and pumpkin seeds.