Fish Stew with Aïoli (Bourride)
Make the aïoli: Whisk lemon juice, garlic, egg yolk, and salt in a heatproof bowl set over a saucepan of simmering water until thick, 2-3 minutes; transfer to a blender. With the motor running, drizzle in oil until sauce is emulsified. Transfer aïoli to a bowl; set aside.
Make the soup: Heat oil in a 6-qt. saucepan over medium heat. Add fennel, cayenne, garlic, leeks, onions, tomatoes, and bay leaf; cook until soft, about 15 minutes. Add wine; simmer until reduced by half, 4-5 minutes. Add stock and 2 cups water; boil. Reduce heat to medium; cook until broth is slightly reduced, 12-15 minutes. Strain broth; return to saucepan over medium heat. Add fish, shrimp, saffron, salt, and pepper; cook until fish is firm and shrimp are pink, 2-3 minutes. Using a slotted spoon, divide fish and shrimp between 6 bowls.
Whisk 0.5 cup broth into aïoli; return to pan. Cook until slightly thick, 4-5 minutes; ladle over fish. Garnish with parsley; serve with toasted baguette.