Cauliflower soup can be excellent, but it needs a little help. Boiled cauliflower tends to give you a pale bowl in more ways than one. Roast it until the edges brown and suddenly it has the nutty, sweet flavour this soup needs.

Leeks bring gentle onion flavour, a small Yukon Gold potato gives the purée body, and aged cheddar adds a sharp finish without requiring a mountain of cheese. Dijon and a little cider vinegar keep the final bowl lively.

🏅 Freezer Hero: freeze the blended soup base, then add milk and cheddar as you reheat each portion.

At a glance

  • Preparation: 20 minutes
  • Cooking: 40 minutes
  • Total time: 1 hour
  • Servings: 6
  • Difficulty: Easy
  • Freezer rating: Excellent when frozen before the dairy goes in
  • Best season: Autumn through early spring

Ingredients — 6 servings

  • 2 large heads cauliflower, about 3 lb / 1.35 kg total, cut into florets
  • 2½ tbsp extra-virgin olive oil, divided
  • 2 large leeks, white and pale green parts only
  • 3 garlic cloves, minced
  • 1 medium Yukon Gold potato, about 8 oz / 225 g, peeled and diced
  • 1 tsp dried thyme
  • ½ tsp freshly ground black pepper
  • ¼ tsp kosher salt initially, plus more as needed
  • 5 cups low-sodium chicken or vegetable stock
  • 1 bay leaf
  • 1 tsp Dijon mustard
  • 1 cup milk
  • 1¼ cups / about 125 g grated aged cheddar
  • 2 tsp apple cider vinegar
  • 2 tbsp chopped fresh chives

Ingredients — 12 servings

Use an 8-quart or larger stockpot and two large baking sheets.

  • 4 large heads cauliflower, about 6 lb / 2.7 kg total, cut into florets
  • 5 tbsp extra-virgin olive oil, divided
  • 4 large leeks, white and pale green parts only
  • 6 garlic cloves, minced
  • 2 medium Yukon Gold potatoes, about 1 lb / 450 g total, peeled and diced
  • 1¾ tsp dried thyme
  • 1 tsp freshly ground black pepper
  • ½ tsp kosher salt initially, plus more after tasting
  • 10 cups low-sodium chicken or vegetable stock
  • 2 bay leaves
  • 1¾ tsp Dijon mustard
  • 2 cups milk
  • 2 cups / about 200 g grated aged cheddar initially, adding more only if needed
  • 1 tbsp apple cider vinegar initially, plus more to taste
  • ¼ cup chopped fresh chives

Method

  1. Roast the cauliflower. Heat the oven to 425°F / 220°C. Spread the florets over one large rimmed sheet, or two for the 12-serving batch. Toss with about two-thirds of the olive oil, a small pinch of salt and some of the black pepper. Arrange in one layer.
  2. Roast for 25–30 minutes, turning once, until tender with plenty of deep golden edges. A few dark brown spots are welcome.
  3. Clean the leeks. Slice lengthwise, then into thin half-moons. Swish the slices in a bowl of cold water; let the grit settle and lift the leeks out of the water. Drain well.
  4. Soften the leeks. Heat the remaining olive oil in a heavy soup pot over medium heat. Cook the leeks for 7–9 minutes, stirring occasionally, until soft and silky but not browned.
  5. Add garlic and thyme. Cook for about 45 seconds, just until fragrant.
  6. Cook the potato. Add the diced potato, stock, bay leaf, remaining pepper and initial salt. Bring to a gentle boil, then simmer for 12–15 minutes, until a knife slides easily through the potato.
  7. Reserve the texture. Set aside about 2 cups of the best-looking roasted cauliflower florets. Add the rest to the pot and simmer for 5 minutes.
  8. Blend. Remove the bay leaf, stir in Dijon and purée until very smooth with an immersion blender. For a countertop blender, work carefully in batches and leave room for steam.
  9. Add the dairy gently. Return the pot to low heat and stir in the milk. Once hot but not boiling, add grated cheddar a handful at a time, stirring until each addition melts. Do not boil after adding cheese; high heat can make it grainy.
  10. Finish. Stir the reserved florets back into the soup. Remove from the heat, add the cider vinegar and taste before adding salt. Serve with chives and more black pepper.

The flavour finish

That little splash of cider vinegar is worth keeping. Cauliflower, potato, milk and cheese all have soft, rounded flavours; a bit of acidity makes the cheddar taste sharper and the roasted vegetables more noticeable.

Stir it in off the heat, wait a few seconds and taste. Add another tiny splash if the soup seems rich but flat.

Taste for acidity before adding more salt.

Easy variations

  • More protein: Blend one drained, rinsed 540 mL / 19 oz can of cannellini beans into the six-serving batch with the cauliflower.
  • Lower-carb: Leave out the potato and add about 2 more cups cauliflower. The soup will be a little less silky.
  • Dairy-free: Omit milk and cheddar, add 1 extra cup stock and blend in ½ cup unsalted cashews soaked in hot water for 20 minutes. Add nutritional yeast to taste, if you like.
  • Broccoli-cauliflower: Replace about one-third of the cauliflower with broccoli and roast it on a separate sheet, as it may brown sooner.
  • Gluten-free: Use certified gluten-free stock, mustard and other packaged ingredients as needed.

Freezer notes

For the smoothest result, stop after blending the cauliflower, leeks, potato, stock and Dijon. Portion off anything you plan to freeze before adding the milk, cheddar, reserved roasted florets, vinegar or chives.

Cool promptly in smaller containers rather than leaving a large stockpot at room temperature. Portion about 2½–3 cups per container for a convenient two-person meal, leaving roughly ½ inch of headspace. Freeze for up to 3 months for best quality.

Thaw overnight in the refrigerator and reheat the base until steaming. Reduce the heat to low, add the appropriate share of milk and finely grated cheddar, and stir until smooth. Finish with fresh vinegar, chives and, if saved separately, roasted florets.

If you have already added cheese, the soup can still be frozen. Reheat slowly without boiling; it may be a little less silky.

Freezer rating: Excellent when you save the dairy finish for serving day.

Batch-cooking tip

For twelve servings, roast on two sheets while the leeks and potato cook. Rotate the pans halfway through if your oven browns unevenly.

You can roast cauliflower a day ahead and refrigerate it. If half the batch is for the freezer, remove that half right after blending and add milk and cheddar only to what you're serving now.

What to serve with it

  • Whole-grain sourdough toast
  • Apple, walnut and arugula salad
  • Turkey and Dijon sandwich
  • Roasted Brussels sprouts with lemon

Nutrition snapshot

Estimated per serving: about 350 calories, 17 g protein, 34 g carbohydrates, 8 g fibre and 18 g fat. Values vary with the cauliflower, cheddar, milk, stock and serving size.

For less sodium, use unsalted or very low-sodium stock and season the roasted cauliflower lightly. Taste after the cheddar, Dijon and vinegar go in before deciding whether more salt is needed.

Cook’s note

Cheddar melts well into hot soup, but a boil can tighten its proteins and separate its fat, leaving the broth grainy. Turn down the heat, grate the cheese finely and add it gradually. Let the heat already in the pot do most of the work.