1In a large pot, melt the butter over medium heat.
Add the onions and celery, and cook until they are soft and translucent, about 5 minutes.
Stir in the flour and cook for another 2 minutes to form a roux.
Gradually add the milk, stirring constantly to avoid lumps.
Add the potatoes and bring the mixture to a boil. Reduce the heat and simmer until the potatoes are tender, about 15 minutes.
Add the clams, heavy cream, salt, and black pepper. Stir well to combine.
Simmer for an additional 5-10 minutes, allowing the flavors to meld together.
Taste and adjust seasoning if necessary.
Serve hot, garnished with fresh parsley if desired.