1. Melt the butter in a stockpot over medium-high heat. Add the leek, onion and carrot and cook, stirring occasionally, for 10 minutes. Stir in the tarragon and thyme and cook 1 minute longer.
2. Add the flour and cook, stirring constantly, for 1 minute. Reduce the heat to medium and gradually stir in the wine and chicken stock. Season the soup with salt and white pepper and add the cauliflower flowerets. Simmer the soup uncovered, stirring occasionally for 30 minutes.
3. Puree the soup in batches in a blender and return to the pot. Stir in the milk and cream. Gently heat just until heated through. Serve hot. Makes 2 1/2 quarts.
Variation: Cauliflower Cheese Stir cheese into soup after milk and cream have been added and heat until the cheese is melted.