The parsley, thyme, and bay leaf bundle is classically referred to as a bouquet garni. When the stew is done, it's removed from the broth.
3 cups chopped onion, divided
1 cup dry white wine
30 medium mussels (about 1 1/2 pounds), scrubbed and debearded
6 flat-leaf parsley sprigs, divided
2 tablespoons butter
2 1/2 cups finely chopped fennel bulb
2 cups finely chopped leeks (about 1 pound)
4 cups boiling water
2 extralarge fish-flavored bouillon cubes (such as Knorr)
3 thyme sprigs
1 bay leaf
1/2 cup half-and-half
1/4 cup crème fraîche
2 large egg yolks
1 3/4 pounds cod or other firm white fish fillets, cut into 1-inch pieces
12 ounces sea scallops
1/4 cup chopped fresh flat-leaf parsley
1 tablespoon (1-inch) julienne-cut lemon rind
1/2 teaspoon sea salt
1/4 teaspoon black pepper
How to Make It
Combine 1 1/2 cups onion, wine, mussels, and 3 parsley sprigs in a Dutch oven; bring to a boil over medium-high heat. Cover and cook 2 minutes or until mussels open; discard any unopened shells. Remove mussels with a slotted spoon; set aside. Strain cooking liquid through a sieve into a bowl, reserving liquid, and discard solids. Remove meat from mussels. Discard shells.
Place Dutch oven over medium heat; melt butter. Add 1 1/2 cups onion, fennel, and leeks; cook 10 minutes or until tender, stirring occasionally. Combine water and bouillon, stirring until bouillon cubes dissolve. Add bouillon mixture and reserved cooking liquid to onion mixture, stirring to combine.
Place the remaining 3 parsley sprigs, thyme, and bay leaf on a double layer of cheesecloth. Gather the edges of the cheesecloth together, and tie securely. Combine the cheesecloth bag and broth mixture; bring to a boil. Reduce heat, and simmer 10 minutes. Remove bag, and discard.
Combine the half-and-half, crème fraîche, and egg yolks in a medium bowl, stirring well with a whisk. Gradually add 1 1/2 cups hot broth mixture to egg mixture, stirring constantly with a whisk. Return egg mixture to pan. Cook 5 minutes or until soup thickens slightly (do not boil), stirring constantly. Add fish and scallops; cook 5 minutes or until fish is done, stirring frequently. Stir in mussels, 1/4 cup chopped parsley, and lemon rind; cook 1 minute or until thoroughly heated. Stir in salt and pepper.