Easy Clam Chowder with Smoked Oysters

Name: Easy Clam Chowder with Smoked Oysters
Ingredients: 1 tablespoon butter or olive oil; 1 yellow onion, diced; 1 teaspoon sea salt, plus more to taste; 2-3 sprigs rosemary; 2 sprigs thyme (optional); 2 bay leaves; 1 cup dry white wine; 4 cups seafood stock OR 3 cups vegetable broth and 1 cup clam juice; 3 large baking potatoes, peeled (optional) and diced; 1/2 cup heavy cream; 1/2 cup milk; 3 stalks celery, sliced; 2 cans clams, chopped (about 6oz); 1 tin smoked oysters, drained from oil (about 3oz); fresh basil, as optional garnish