In a medium pot, cook the chopped bacon over medium heat until crispy. Remove the bacon and set it aside, draining any excess fat from the pot.
Add butter to the same pot, then sauté the onion and garlic until softened and fragrant.
Stir in the diced celery, carrots, and corn. Cook for 2-3 minutes until the vegetables begin to soften.
Sprinkle the flour over the vegetables and stir to coat them evenly.
Add the diced potato, bay leaf, and mussel broth (or fish stock). Add water as needed to cover the vegetables. Bring the mixture to a boil, then reduce heat and let it simmer until the potatoes are tender, about 10-15 minutes.
Stir in the heavy cream and smoked salmon slices. Simmer for an additional 5 minutes, letting the flavors meld.
If using mussels, add them to the pot during the last 3-4 minutes of cooking. Cover and cook until the mussels open. Discard any that don’t open.
Season with salt, pepper, and garnish with fresh thyme or parsley if desired. Serve hot with the reserved crispy bacon sprinkled on top.