- 1 large leek, green part coarsely chopped and white part cut into 1/4-inch pieces
- 5 tablespoons olive oil
- 1 medium onion, coarsely chopped
- 2 celery ribs, coarsely chopped
- 2 carrots, coarsely chopped
- 3 garlic cloves, smashed
- 1/4 teaspoon crumbled saffron threads
- 2 bay leaves (not California)
- 1 teaspoon dried hot red pepper flakes
- 1 1/4 lb plum tomatoes, coarsely chopped
- 3 tablespoons canned tomato purée
- 2 cups dry white wine
- 1 1/2 qt white fish stock
- 1 (8- to 9-inch) unsliced round or oval pain au levain or sourdough loaf (1 lb), crust discarded
- 2 tablespoons unsalted butter
- 1 lb skinned white fish fillets such as halibut, snapper, and/or bass, cut into 1-inch cubes
- 1 teaspoon salt
- 2 cups rouille
- 1 tablespoon chopped fresh oregano
- 1 tablespoon chopped fresh flat-leaf parsley
- Wash green and white parts of leek separately in a bowl of cold water, then lift out with a slotted spoon and pat dry. Heat 3 tablespoons oil in a 6-quart heavy pot over moderate heat until hot but not smoking, then cook leek greens, onion, celery, and carrots, stirring, until beginning to soften, about 5 minutes. Add garlic and cook, stirring, 3 minutes. Add saffron, bay leaves, and red pepper flakes and cook, stirring, 2 minutes. Add fresh tomatoes and tomato purée and cook, stirring, 4 minutes. Add wine and simmer, uncovered, until liquid is reduced by about half, about 30 minutes.
- Stir in stock and bring to a boil. Reduce heat and simmer, uncovered, 30 minutes. Carefully pour through a fine sieve into a bowl, then discard solids.
- Preheat oven to 300°F.
- Heat a well-seasoned ridged grill pan over moderately high heat until hot. Brush bread with remaining 2 tablespoons oil, then grill on all sides until grill marks appear. Tear bread into rough 3-inch pieces and bake on a baking sheet in middle of oven until crisp outside but soft inside, about 10 minutes. Cool croûtes.
- Heat butter in a 4-quart heavy saucepan over moderate heat until foam subsides, then cook white part of leek, stirring, until beginning to soften, about 2 minutes. Add fish, hot broth, and salt and bring to a simmer (fish will be cooked through). Remove from heat and stir in 1/2 cup rouille.
- Put croûtes in soup plates and ladle soup over. Sprinkle with oregano and parsley and serve remaining rouille on the side.