Place the clams and 1 tablespoon water in a saucepan, cover, and steam over high heat until the clams open, 4 to 5 minutes. Set aside 8 clams in their shells for garnish. Remove the remaining clams from their shells. (Discard any clams that do not open.) Strain the liquid from the pot through a fine-mesh sieve set over a bowl, and set the broth aside.

Put the bacon and canola oil in a large, heavy-bottomed pot and saute over medium-low heat until the bacon is browned and crisp and has rendered some fat, about 6 minutes. Use tongs or a slotted spoon to transfer the bacon to a paper towel-lined plate.

Add the onions to the pot and saute until they are softened but not browned, about 4 minutes. Add the leeks and garlic, and saute until softened but not browned, about 2 minutes. Return the bacon to the pot and add the potatoes, cream, and reserved clam juice. Lightly season the contents of the pot with salt and pepper. Raise the heat to high, bring the broth to a boil, then lower the heat and let it simmer for 10 minutes.

Remove the pot from the heat. Return the shelled and unshelled clams to the pot, and season to taste. Cover the pot to keep the sauce warm.

Heat the olive oil in a wide, deep saute pan set over medium heat. Season the cod fillets with salt and pepper, and put them in the pan, skin side down, without crowding. Cook until golden, about 4 minutes, then turn and cook about 3 minutes more, depending on the thickness of the fish.

To serve, transfer the fillets to a warmed serving platter, and spoon the sauce over and around the fish. Arrange the unshelled clams around and on top of the fish, and scatter the parsley over the top.

Variations

Substitute other firm whitefish, such as halibut or bass.

Use salt pork in place of the bacon for a more traditional New England chowder flavor.