Soup is such great comfort food on a cold, stormy day — and we just love this combination of mellow, earthy cauliflower and nutty Gruyére cheese. It's equally delicious with sharp white cheddar, if you prefer. We like to purée about half of the soup and leave the other half chunky, but there's no hard-and-fast rule here.
Serve piping hot with crusty bread and a green salad for a satisfying lunch or light supper.
Melt the butter in a large saucepan over medium heat, and add the onion and celery. Cook, covered, until the vegetables are soft, about 10 minutes.
Stir in the flour, mustard powder and paprika, and cook, stirring frequently, for 2 minutes to form a roux. Slowly whisk in the wine and chicken stock, whisking until smooth. Add the cauliflower, cover the pan and bring the mixture to the start of a simmer over medium-high heat.
Reduce the heat to maintain a gentle simmer, cover the pan, and cook until the cauliflower is soft, about 20 minutes. Remove the lid and let the soup cool slightly.
Transfer half of the soup to a food processor and purée until smooth. Add the purée to the soup in the saucepan and return the pan to low heat. Add the cheese and half & half, and simmer until the cheese melts and the soup is heated through — but don't allow the soup to boil! Season with salt and pepper to taste, and serve hot.