Preparation Mix mayonnaise, garlic, and cayenne in small bowl. Cover and chill rouille. (Can be prepared 1 day ahead.) Place fennel fronds, thyme sprigs, and orange peel on large square of 2 layers of moistened cheesecloth. Gather cheesecloth and tie securely. Heat 2 tablespoons oil in heavy large pot over medium-high heat. Add fennel bulb and leek and sauté until soft, about 8 minutes. Add wine and saffron; bring to boil. Add broth and bouquet garni; return to boil. Cover, reduce heat to medium-low, and simmer 45 minutes. Add fish and simmer until opaque in center, about 5 minutes. Meanwhile, preheat oven to 375°F. Brush baguette slices with remaining 1 tablespoon oil. Arrange on baking sheet. Bake until golden brown, about 8 minutes. Spread rouille on toasts. Ladle stew into wide soup bowls, top with toasts, and serve.
Preparation Mix mayonnaise, garlic, and cayenne in small bowl. Cover and chill rouille. (Can be prepared 1 day ahead.) Place fennel fronds, thyme sprigs, and orange peel on large square of 2 layers of moistened cheesecloth. Gather cheesecloth and tie securely. Heat 2 tablespoons oil in heavy large pot over medium-high heat. Add fennel bulb and leek and sauté until soft, about 8 minutes. Add wine and saffron; bring to boil. Add broth and bouquet garni; return to boil. Cover, reduce heat to medium-low, and simmer 45 minutes. Add fish and simmer until opaque in center, about 5 minutes. Meanwhile, preheat oven to 375°F. Brush baguette slices with remaining 1 tablespoon oil. Arrange on baking sheet. Bake until golden brown, about 8 minutes. Spread rouille on toasts. Ladle stew into wide soup bowls, top with toasts, and serve.