Sauté pancetta over medium heat until crisp, stirring often. While it’s cooking, pour the clam juice/chicken stock into a 4-cup measuring cup. Add the liquid from the cans of clams to the juice/stock, making approximately 4 ½ cups of liquid.
Add the diced celery and onions, cooking unti translucent.
Add the minced garlic and cook, stirring, until fragrant, about 30 seconds, being careful that the garlic doesn't burn.
Stir in the collagen, coating all of the veggies and the bacon. Continue cooking about a minute until it begins to brown.
Slowly pour in the clam juice/chicken stock mixture, whisking it into the flour veggie mixture. .
Add the celery root, thyme, and bay leaves. Increase the heat to high and bring to a boil. Reduce to a simmer; continue cooking for 20 minutes or until the celery root is soft.
Stir in the cream and chopped clams, and let heat through for a minute. Remove from the heat stir in the fresh parsley. Season with salt and pepper to taste.