Step 1

Melt butter in heavy medium skillet over medium heat. Add fennel and sauté until golden, about 10 minutes. Add 1 cup water; cover and cook until fennel is very tender, about 20 minutes. Puree fennel mixture in processor. Set aside.

Step 2

Heat oil in heavy large saucepan over medium heat. Add garlic and saffron; sauté 1 minute. Add clam juice, cream, and Pernod and bring to simmer. Add fennel puree and bring to simmer. DO AHEAD Can be made 1 day ahead. Refrigerate uncovered until cold. Cover and keep refrigerated. Simmer before continuing. Add oysters with their liquor to cream mixture and stir to heat through. Ladle soup into bowls.