Melt the butter in a Dutch oven set over medium heat. Add the bacon and fry until golden and crisp, 6-8 minutes; remove to a plate lined with paper towels and cover with aluminum foil.
Add the onion, celery, garlic, potatoes, and a pinch of salt to the Dutch oven, sweating until starting to color, about 10 minutes.
Whisk in the cornstarch and cook for 2 minutes; whisk in the milk followed by the stock in a slow, steady stream until fully incorporated.
Add the bay leaves and bring the mixture to a simmer; cook steadily until the potatoes are very soft, 15-20 minutes.
Discard the bay leaves. Whisk in the cream; bring the chowder to a simmer and season to taste with salt and pepper; keep warm over very low heat.
Place the clams in a large saucepan set over high heat. Add the wine, cover the pan with a lid, and cook until the clams have steamed open, 3-4 minutes; discard any that don't open.
Drain the clams and leave to cool for 3 minutes. Pick the meat from the shells; stir the picked clam meat into the chowder along with the parsley and reserved bacon.
Serve straight away for best results.
