In a large soup pot or Dutch oven, cook the bacon over medium heat until fat has rendered and the bacon is crisp. Transfer the bacon to a plate, but leave the fat. (Use bacon in another recipe or as a cook’s snack).
Add the chopped onion, carrots and celery to the bacon fat. Cook, stirring often, until the onions begin to soften; 6 to 8 minutes. Add fish bones, shrimp shells and tails, garlic, thyme, bay leaves, peppercorns, wine and 10 cups of water.
Bring to a simmer. Cook, at a low simmer for 30 minutes, removing any scum that rises to the top. Strain then use immediately or refrigerate in a tightly covered container up to 2 days or in the freezer for several months.
For the stew
In a wide pot or Dutch oven, melt the butter over medium heat. Add onion, fennel and celery. Add a pinch of salt and cook, stirring often until softened and sweet, 6 to 8 minutes. Add the garlic and cook 1 minute then stir in 5 cups of fish stock.
Bring the stock to a simmer then add the clams cover, and cook for 3 minutes.
Meanwhile, season the shrimp and fish with salt and pepper.
Stir in the shrimp and mussels. Arrange the fish on top of the stew, cover, and simmer until shellfish opens and the fish and shrimp are firm and opaque, about 5 minutes more. Stir in the greens and cook until wilted, about 1 minute.
Remove the pot from the heat then swirl in the cream. Taste for seasoning and adjust with more salt and pepper. Serve divided between bowls with bread for dipping and lemon wedges on the side.
