Place the clams and 1 or 2 cups of water in a large pot. Cover and place over high heat. Cook the clams for 6 to 7 minutes. Take off the cover and place the open clams in a large bowl. Cover the pot again and continue cooking the clams that haven’t opened yet. Return the cover and continue cooking the remaining clams for another 2-3 minutes. Discard any of the clams that have not opened and add the opened clams to the large bowl.
Strain the liquid from the pot and reserve.
Coarsely chop the clams and reserve.
Rinse/clean and dry the large pot used to cook the clams. Now add approximately 1 to 2 teaspoons of olive oil to the bottom of the clam pot and add the bacon. Bring the pan to a medium heat and cook the bacon until it is brown and crispy.
Using a slotted spoon remove the bacon and set aside.
Add the onions and celery to the pot and cook until they are soft, but not browned (7-8 minutestirring often. Add the leaks and garlic to the mixture and cook for another 2-3 minutes.
Stir in the potatoes and wine and continue cooking until the potatoes have just started to soften, approximately 5 minutes.
Add the reserved clam juice ensuring the potato and onion mixture is covered with liquid. Add the thyme and bay leaf.
Stir cornstarch and 2 tablespoons of water in a small bowl to form a slurry. Stir it into the chowder base and return to boil and thicken.
When the potatoes are tender and the base has thickened, add the cream and stir in the chopped clams. Depending on how much you enjoy a bacon flavor to your chowder, you can add either some or all of the reserved bacon.
Add ground black pepper to taste. Let it come back to a simmer and remove it from the heat. Remove the bayleaf.
Allow the chowder to sit for a while before serving (approximately 30 minute and then reheat. Garnish with chopped chive.