How to Make It
In a large enameled cast-iron casserole, heat the oil. Add the bacon and cook over moderate heat until crisp. Add the onion and cook until beginning to brown, about 5 minutes. Whisk in the flour and cook until lightly browned, about 2 minutes. Whisk in the fish stock and bring to a simmer. Add the potatoes, turnips, parsnips, celery root and thyme and simmer over moderate heat until tender, about 20 minutes.
Add the milk and cook, stirring occasionally, until the soup is thickened, about 10 minutes. Stir in the snapper, lemon juice, Worcestershire and a dash of hot sauce and cook until the fish is just white throughout, about 5 minutes. Stir in the parsley and season with salt and pepper. Transfer the chowder to bowls and garnish with dill. Serve, passing more hot sauce at the table.