In a large Dutch oven or heavy pot, cook the chopped bacon over medium heat until crispy, about 5-7 minutes. Remove with a slotted spoon and set aside, leaving the bacon fat in the pot.
Add butter to the bacon fat. Once melted, add the diced onion and celery. Sauté for 5 minutes until softened, then add the garlic and cook for another minute until fragrant.
Sprinkle the flour over the vegetables and stir well to coat everything. Cook for 2 minutes, stirring constantly, to remove the raw flour taste.
Gradually pour in the stock while whisking to prevent lumps. Add the diced potatoes and thyme, then bring to a boil. Reduce heat and simmer for 15 minutes until the potatoes are tender.
Add the clams with their juice and the heavy cream. Stir in the cooked bacon, reserving a little for garnish. Heat through gently for 5 minutes—don't let it boil or the cream might curdle.
Season with salt and pepper to taste. Ladle into bowls and top with reserved bacon and fresh parsley. Serve with crusty bread for dipping!
