Sauté the Vegetables:In a large pot, melt the butter over medium heat. Add the diced onion, celery, carrot (if using), and garlic. Sauté for about 5-7 minutes until the vegetables are softened and fragrant.
Add the Broth and Potatoes:Pour in the chicken broth and add the diced potatoes. Bring the mixture to a boil, then reduce the heat and simmer for 15-20 minutes, or until the potatoes are tender.
Add the Seafood:Once the potatoes are tender, add the shrimp, fish, scallops, and clams. Stir gently and cook for an additional 5-7 minutes, until the seafood is cooked through.
Stir in Cream and Seasonings:Lower the heat and stir in the heavy cream, milk, bay leaves, thyme, and salt and pepper. Simmer for another 5 minutes to allow the flavors to meld together.
Garnish and Serve:Remove the chowder from heat and discard the bay leaves. Ladle the chowder into bowls and garnish with freshly chopped parsley and bacon (optional). Serve with crusty bread or crackers for dipping.