This recipe from Boston chef Jasper White gets its creamy thickness from heavy cream and the starch in the potatoes.
Scrub individually with a vegetable brush:
5 pounds quahogs or other hard-shell clams
Place in a sink or large soup pot, cover with cold water, and stir in:
1/4 cup salt
Let stand for 30 minutes to rid the clams of sand. Rinse and drain in a colander. Place the clams in a large soup pot and add:
1 cup water
Any scraps of onion, celery, thyme, or bay leaf (optional)
Cover and steam over high heat until the clams are completely open, 10 to 15 minutes. Discard any that do not open. Pour the cooking liquid through a fine-mesh sieve and set aside. When the clams are cool enough to handle, remove from their shells and coarsely chop into 3/8" inch pieces.
Place in a soup pot and cook, stirring, over medium heat until slightly crisp:
2 slices bacon or 2 ounces salt pork, diced
Stir in:
1 medium onion, cut into 1/2-inch dice
1 bay leaf
1/2 tablespoon chopped fresh thyme
1 tablespoon unsalted butter
When the onions are translucent, add the reserved cooking liquid along with:
3 red or white new potatoes, cut into 1/2-inch dice
Bring to a boil, reduce the heat, and simmer until the potatoes are tender, about 12 minutes. Stir in the chopped clams along with:
