This rich stew from Boston chef Matt Jennings gets exceptional flavor from smoked mussels. Slideshow: More Holiday Hor d'Oeuvres Recipes
Preheat the oven to 375°. On one side of a large rimmed baking sheet, toss the potatoes with 2 tablespoons of the olive oil and season with salt and pepper. On the other side of the baking sheet, toss the brussels sprouts with the remaining 1 tablespoon of olive oil and season with salt and pepper. Roast for about 25 minutes, until the vegetables are tender and charred in spots.
Meanwhile, in a large saucepan, combine the fresh mussels with the wine, onion, shallots, butter, parsley sprigs, thyme, bay leaf and cayenne and bring to a boil over high heat. Cover and cook over moderately high heat until the mussels open, 6 to 8 minutes. Using a slotted spoon, transfer the mussels to a bowl. Remove the mussels from their shells; discard the shells and any mussels that do not open. Strain the broth through a fine sieve.
Wipe out the saucepan. Add the strained broth along with any accumulated mussel broth from the bowl and bring to a boil. Add the cream and bring just to a boil. In a small bowl, beat the egg yolk with 2 tablespoons of the hot cream, then gradually whisk the mixture into the saucepan. Simmer the soup over moderate heat, whisking, until thickened slightly, 3 to 5 minutes. Stir in the brussels sprouts, potatoes and both the cooked mussels and the smoked mussels and simmer until hot, about 3 minutes. Stir in the lemon juice and season with salt and pepper. Serve the stew in small ramekins, garnished with chopped parsley.
The soup can be refrigerated overnight. Reheat gently before serving