Drain clam juice from cans into a liquid measuring cup. Add enough bottled clam juice to equal 2 ½ cups. Set aside. (See directions in Notes if using fresh clams.)
In a Dutch oven, cook bacon over medium heat until fat is rendered and slightly brown. Remove half of the bacon with a slotted spoon to a paper towel lined plate. Drain off all but 2 tablespoons grease. To the remaining bacon and drippings, melt in 1 tablespoon butter over medium heat.
Increase heat to medium high and add celery and onion. Sauté for 5-7 minutes or until onions are soft. Add potatoes, garlic, red pepper (if using) and sauté 30 seconds. Sprinkle in flour and cook an additional 1 minute. Stir in chicken broth, reserved 2 ½ cups clam juice, chicken bouillon, bay leaves and all seasonings. Bring to a boil then reduce to a simmer. Simmer, uncovered, for 15-20 minutes or until potatoes are very tender.
Stir in heavy cream and bring to a simmer to heat through. Discard bay leaves. Remove from heat and stir in clams. Taste and add salt/pepper to taste. (You may or may not need additional salt depending on how salty your clams and bacon are.) For a thinner or less chunky soup stir in additional heavy cream/milk or chicken broth.
Top individual servings with reserved bacon and oyster crackers and fresh parsley if desired.
