Cioppino (San Francisco Seafood Stew)

For the Seafood Stock: In a large, 8- or 12-quart heavy-bottomed pot, heat olive oil over medium-high heat until shimmering. Add onion, fennel, celery, and garlic, and cook, stirring, until softened and beginning to brown, about 7 minutes. Stir in tomato paste and cook for 1 minute.

Add crabs (if using) and shrimp shells, and cook, stirring and scraping often, until shells are cooked through and turning red, 3 to 4 minutes.

Add white wine, bring to a boil, then cook until raw alcohol smell is gone, about 4 minutes. Add fish heads and bones along with the clam juice. Cover with water (at least 2 1/2 quarts). Add parsley, bay leaves, and black peppercorns. Bring to a boil, reduce heat to a simmer over medium low heat, and cook for 1 hour. Strain seafood stock and reserve until ready to make cioppino. You should have about 2 quarts (1.9L); add enough water to bring total volume of the stock up to 2 1/2 quarts (2.4L), then set aside.

Meanwhile, for the Roasted Red Pepper Salsa: Working directly over the flame of a gas burner or under a broiler, cook the red bell peppers, using tongs to turn occasionally, until deeply charred all over, about 10 minutes. Transfer to a heatproof bowl, cover with plastic, and let stand 5 minutes.

Using paper towels, rub charred skin off peppers. Stem and seed peppers, then roughly chop flesh and add to a blender jar or tall, narrow vessel compatible with an immersion blender.

Add olive oil, lemon juice, chile paste and minced fresh herbs and, using an immersion blender, blitz until fairly smooth. Stir in salt, then set aside or refrigerate for up to 5 days until ready to use.

For the Cioppino: In a large 8- or 12-quart, heavy bottomed pot, heat olive oil over medium heat until shimmering. Add onion, fennel, garlic, red pepper flakes, and chile paste (if using). Season with 2 teaspoons salt, and cook, stirring often, until very soft but not browned, about 15 minutes; lower heat if necessary to prevent browning.

Add crushed tomatoes and their juices along with the 2 1/2 quarts (2.4L) Seafood Stock. Bring to a simmer over medium heat. Add squid and cook at a gentle simmer over medium low heat  for 18 minutes. Increase heat to medium high; add mussels and and clams. Bring to a simmer and reduce heat to medium; cook until they just begin to pop open, about 3 minutes. Season halibut with 3/4 teaspoon salt, gently add to broth, cook for 2 minutes. Season shrimp with 1/2 teaspoon salt, then add to broth, cook until shrimp is just pink and halibut is just cooked through, about 1 minute. Remove from heat, all the mussels and clams should be open (discard any that are unopened). Using tongs and a spider or slotted spoon, pick out 20 mussels and transfer to a medium bowl. Shell the mussels, add the mussels back into the broth, and discard the shells. Season broth with remaining 3/4 teaspoon salt.

If using crabmeat, add to a strainer and lower into the simmering broth until just warmed through, about 30 seconds, then remove and arrange on a small serving bowl. Divide stew among bowls. Garnish with reserved fennel fronds, and serve with toasted sourdough, the Roasted Red Pepper Salsa, and warmed crab (if using).