In a large saucepan, melt the butter over medium-high heat. Add the onions and cook, stirring, until just beginning to caramelize, about 10 minutes. Add the garlic and cook, stirring, for 30 seconds. Add the potatoes, salt, pepper, cayenne, and bay leaf, and cook, stirring, for 3 minutes. Add the stock and bring to a boil. Reduce the heat to medium-low and simmer, covered, until the potatoes are tender, about 25 to 30 minutes.
Remove and discard the bay leaf. Remove from the heat and puree with a hand-held immersion blender, or in batches in a food processor, until smooth. Add the light and heavy creams, and stir well to blend. Gently reheat and barely simmer, being careful not to boil. Add 3/4 cup of the cheese, the thyme, and Port, and whisk until the cheese is just melted. Adjust the seasonings, to taste.
Ladle the soup into bowls, and top each with some of the remaining 1/4 cup of cheese and the crumbled bacon. Serve immediately with the Blue Cheese and Walnut Crumpets.
Yield: 8 servings