For the fish stock: Heat a stockpot, lightly coated with olive oil, over medium heat. Add the onion, celery, garlic and some salt, and sweat for 3 to 4 minutes. Stir in the fish bones and shrimp shells, and fill the pot with water. Add the bay leaves and thyme and bring to a boil. Lower the heat and simmer for 20 minutes. Strain the liquid into a bowl and reserve. Voila! Fish stock!
For the tomato broth: Lightly coat a large saucepan with olive oil and heat over medium heat. Add the onion, fennel, celery and a large pinch of salt. Cook the veggies until soft and very aromatic, 8 to 10 minutes. Add the garlic and crushed red pepper and cook for another 3 to 4 minutes. Stir in the wine and reduce by half. Season with salt. (It's important to season all along the way.)
Add 8 cups of the fish stock and the saffron. Stir in the tomatoes, thyme and bay leaves. Season with salt and cook for 20 to 30 minutes. The final broth should be a very pretty and flavorful soup. Taste and add salt as needed. Remove and discard the thyme bundle and bay leaves.
For the stew: Heat a straight-sided saute pan, lightly coated with olive oil, over high heat. Sprinkle the cod with salt, add it to the pan and brown it on all sides. Remove to a large plate and reserve.
Drain the fat from the pan and add the clams and about 4 cups of the tomato broth. Cover and cook until the clams open, about 3 to 4 minutes. Add the shrimp and cod along with the beans and the escarole. Cover and cook until the cod and shrimp are cooked through and the escarole is wilted. If at any point the soup has cooked down too much, add more tomato broth.
For the toast: Preheat a grill. Place ciabatta slices on grill and toast on both sides. Remove and rub with garlic. Drizzle with olive oil and cut in half.
To assemble: Remove the cod, clams and shrimp from the pan and put in a bowl. Spoon the beans and escarole into serving bowls. Ladle in the tomato broth and arrange the cod, clams and shrimp on top of the beans and escarole. Drizzle with olive oil and sprinkle with fennel fronds. Serve two grilled bread halves with each serving.