1. In a large pot, heat butter over medium-high heat. Add onion and celery; sauté until softened, stirring often.
2. Stir in the flour to distribute evenly. Add stock, clam juice, heavy cream, bay leaves, and potatoes; stir to combine.
3. Stirring consistently, bring to a simmer. Reduce heat to medium-low and cook 20 minutes, stirring often, until potatoes are tender.
4. Add clams and season to taste with salt and pepper. Cook until clams are just firm, another 2 minutes.