Place clams and mussels in a large pot with shallots, thyme, bay leaf, white peppercorns, white wine and butter.
Cover and bring this to a light boil until the clams and mussels completely open.
Remove from heat and strain liquid through a fine mesh strainer, reserving liquid.
Remove clam meat and mussel meat from shells and set aside.
In a large pot sauté bacon over medium heat for about 3 minutes.
Add diced onion and garlic and sauté for a further 2 minutes.
Add carrots, celery and potatoes.
Add reserved liquid and cream. Allow to simmer until potatoes are fork tender.
Add snapper, salmon, cooked clam and mussel meat. Bring to a simmer and remove from heat.
Adjust seasoning and add lemon juice. Serve in individual soup bowls and garnish with chopped parsley.