Heat the butter in a large pot over medium-high heat. Add the onion and celery and saute until softened, mixing often. Stir in the flour to distribute evenly. Add the stock, juice from 2 cans of chopped clams (reserve clams), cream, bay leaves, and potatoes and stir to combine. Bring to a simmer, stirring consistently (the mixture will thicken), then reduce the heat to medium-low and cook 20 minutes, stirring often, until the potatoes are nice and tender. Then add clams and season to taste with salt and pepper, cook until clams are just firm, another 2 minutes.
Melt the butter in a large skillet and toss the bread cubes in the butter until browned and toasted, about 2 to 3 minutes. Add parsley and season with salt and pepper.