1. Adjust oven rack to lowest position and heat oven to 500°F. Heat oil, leeks, and garlic in large roasting pan over medium heat; cook, stirring occasionally, until leeks are wilted, about 3 minutes. Add Pernod, water, and bay leaves and bring to boil. Cook until liquid is slightly reduced, about 1 minute. Add mussels and salt. Cover pan tightly with aluminum foil and transfer to oven. Cook until most mussels have opened (a few may remain closed), 15 to 18 minutes.

2. Remove pan from oven. Push mussels to sides of pan. Add crème fraîche to center and whisk until incorporated. Discard bay leaves, sprinkle chives over mussels, and toss to combine. Serve immediately.

Serves 2 to 4