- 3 tablespoons olive oil
- 1 yellow onion, sliced
- 1 head cauliflower, chopped
- 2 cups low-sodium chicken broth
- 2 cups whole milk
- 4 small crusty rolls
- 4 ounces sliced prosciutto
- 1 cup watercress, trimmed
- 2 cups (8 ounces) grated white Cheddar
- kosher salt and pepper
- Heat 1 tablespoon of the oil in a saucepan over medium-high heat. Add the onion and cook, stirring, until soft, about 5 minutes.
- Add the cauliflower, broth, and milk and simmer until tender, about 15 minutes.
- Cut the rolls in half. Layer the bottoms with the prosciutto and watercress. Drizzle with 1 tablespoon of the oil. Top with the roll halves.
- Puree the soup in the pan using a handheld immersion blender or, working in batches, a standard blender.
- Stir in 1 ⅔ cups of the Cheddar, 1 teaspoon salt, and ¼ teaspoon pepper.
- Divide the soup into bowls. Add the remaining oil and Cheddar and ¼ teaspoon pepper. Serve with the sandwiches.