Cauliflower Cream Soup with Cheesy Mustard Croûtons

Most permutations of cauliflower (roasted florets, cauliflower rice, yes, even cauliflower gnocchi) rarely tempt me. But when you simmer a whole head of cauliflower with onion, garlic and half-and-half, then blend it all until thick and velvety, it makes a sublime creamy cauliflower soup that’s all the more remarkable because it's so quick to prepare. Half-and-half adds just the right amount of rich dairy flavour to help the cauliflower taste its best, but you could also use milk, heavy cream (or mix equal parts of both for DIY half-and-half), or plant-based milk. Don’t skip the white pepper or the lemon juice, freshly squeezed - they’re the secret ingredients that’ll have you craving spoonful after spoonful. The cheesy mustard croutons on top offer an ideal mix of sharp and rich flavours, but this creamy soup would also be delicious topped with toasted sunflower seeds, a spoonful of chili crisp, or some pesto.

Soup:
3 Tbsp. extra-virgin olive oil, divided
1 medium onion, chopped
1½ tsp. sea salt
3 cloves garlic, finely chopped
1 large head (2½-3 lbs) cauliflower, florets broken into small pieces, core chopped
¼ tsp. white or black pepper, freshly ground
¾ cup half-and-half cream
1 Tbsp. Dijon mustard
1 Tbsp. butter, melted
sea salt
black pepper, freshly ground
1 Tbsp. + 1½ tsp. lemon juice, freshly squeezed

Croûtons:
5 cups Country-style bread, preferably day-old, torn or sliced into 1" cubes
½ cup Gruyère or cheddar, finely grated

Preheat an oven to 350°F (180°C/160°C fan, Gas Mark 4). Place a rack in the middle of the oven. Line a rimmed baking sheet with parchment paper.

Heat 2 Tbsp. extra-virgin olive oil in a large saucepan or small Dutch oven over medium-low. Add the onion and season with sea salt. Cook, stirring occasionally and reducing heat if the onion starts to brown, until softened but without taking on any colour, about 5-7 minutes.

Add garlic and cook, stirring, until softened and fragrant, about 2 minutes. Add the cauliflower florets, pepper and water (the water should just barely cover the cauliflower). Bring to a boil, then reduce the heat and simmer, uncovered, until cauliflower is completely tender and starting to fall apart, about 15-20 minutes. Stir in the half-and-half and simmer for 5 minutes; remove from heat.

Make the Croûtons:
While the soup is simmering, whisk the Dijon mustard, butter and the remaining 1 Tbsp. olive oil in a medium bowl to combine; season with salt and pepper.

Add the bread cubes and toss to coat in mustard mixture. Scatter the Gruyère or cheddar over and toss again to combine. Transfer the bread mixture to the prepared baking sheet and bake in a single layer, turning halfway through, until cheese is melted and the croûtons are golden brown and crisp, about 10-15 minutes.

Assembly:
Working in batches, carefully purée the soup in a blender until very smooth, transferring to a medium bowl as you go. (Alternatively, you can use an immersion blender to blend soup in the pot until smooth.) Return the soup to the pot and reheat over medium-low, stirring and adding more water to thin if needed (you’re going for the consistency of heavy cream). Stir in the lemon juice. Taste and season with more salt and/or pepper if desired.

Ladle soup into bowls. Top with cheesy mustard croûtons and drizzle with more oil.

Makes 4 servings.

Make-Ahead: Soup can be made 3 days ahead. Let cool; cover and chill. Reheat soup over medium-low, adding a splash of water to thin if needed.