How to Make It
Combine clams, 3 cups water, and clam juice in a Dutch oven; bring to a boil over high. Cover and reduce heat to medium-low. Simmer 6 minutes or until clams open. Discard unopened clams. Remove clams; let cool. Remove meat; chop. Discard shells. Pour broth through a cheesecloth-lined strainer; discard solids.
Add bacon to Dutch oven over medium-high; cook until crisp. Remove bacon and crumble. Add butter, onion, and celery to bacon drippings in pan; sauté 8 minutes. Stir in flour and pepper; sauté 1 minute. Add wine; cook 1 minute. Add potatoes and reserved clam broth; bring to a boil. Cover and reduce heat to low. Simmer until potatoes are tender, 15 minutes.
Transfer 1 cup vegetables and liquid to a blender. Remove center piece of lid. Secure lid; place towel over opening. Process until smooth. Return puree to soup; add half-and-half and reserved clams. Return soup to a simmer. Garnish with parsley and bacon.