Source: East Hampton Clam Chowder, Barefoot Contessa Family Style
12 tablespoons (1 ½ sticks) unsalted butter, divided
2 cups chopped yellow onions (2 onions)
2 cups medium-diced celery (4 stalks)
2 cups medium-diced carrots (6 carrots)
4 cups peeled medium-diced boiling potatoes (8 potatoes)
1 ½ teaspoons minced fresh thyme leaves (½ teaspoon dried)
1 teaspoon kosher salt
½ teaspoon freshly ground black pepper
1 quart (4 cups) clam juice
½ cup all-purpose flour
2 cups milk
3 cups chopped fresh chowder clams (1 ½ pounds shucked clams)
Melt 4 tablespoons (½ stick) of the butter in a large heavy-bottomed stockpot. Add the onions and cook over medium-low heat for 10 minutes, or until translucent. Add the celery, carrots, potatoes, thyme, salt, and pepper and saute for 10 more minutes. Add the clam juice, bring to a boil, and simmer, uncovered, until the vegetables are tender, about 20 minutes.
In a small pot, melt the remaining 8 tablespoons of butter and whisk in the flour. Cook over very low heat for 3 minutes, stirring constantly. Whisk in a cup of the hot broth and then pour this mixture back into the cooked vegetables. Simmer for a few minutes until the broth is thickened.
Add the milk and clams and heat gently for a few minutes to cook the clams. Taste for salt and pepper. Serve hot.