Melt the butter or margarine in a stockpot over medium high heat.
Add leek, onion, and carrot; cook, stirring occasionally, for 10
minutes. Stir in the tarragon and thyme; cook 1 minute longer
Add flour; 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. Add the steamed cauliflower
flowerets. Simmer the soup, uncovered, stirring occasionally for 30
minutes.
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.
If you decide to use the Swiss cheese, stir it in and heat until
melted