5 pounds littleneck or cherrystone clams, well scrubbed
2 cups dry white wine, water or fish stock
3 cups bottled clam juice, or fish stock
2 tablespoons olive oil
6 ounces pancetta, or bacon, cut into small pieces
2 yellow onions, chopped
7 small red potatoes, cut into small chunks
1½ cups heavy cream
freshly ground black pepper, to taste
pinch cayenne pepper, optional
2 tablespoons unsalted butter, optional
¼ cup chopped fresh parsley, or chives

In a large, wide saucepan over high heat, combine the clams and the wine, water, or stock.  Then...

1. Cover and cook until the clams open, about 5 minutes. 

2. Using a slotted spoon, transfer the clams to a bowl, Discarding any that did not open. 

3. Strain the cooking liquid through a sieve lined with damp cheesecloth (muslin) placed over a large bowl. 

4. Remove the clams from their shells and chop coarsely, capturing and straining any of the juices. 

5. Measure the cooking liquid and add enough clam juice or fish stock to measure 5 cups.  Set aside.

In a saucepan over medium-low heat, warm the olive oil.  Then...

1. Add the pancetta or bacon and onions and cook, stirring occasionally to prevent sticking, until softened, about 10 minutes. 

2. Raise the heat to high, add the reserved liquid, and bring to a boil. 

3. Add the potatoes and reduce the heat to low. 

4. Cook, uncovered, until the potatoes are firm but almost completely cooked through, 10-15 minutes. 

5. Add the clams and simmer until heated through, about 4 minutes. 

6. Add the cream and season with the black pepper and the cayenne pepper, if using. 

7. Swirl in the butter, if using, and top with the chopped herbs.

Finally...Ladle the chowder into warmed individual bowls and serve immediately.