Steam the clams and reserve the liquid (see instructions below).
Strain the liquid through a cheesecloth to remove the sand and pour it into a large pot. Add enough water to make 2 cups (500 ml). Add the potatoes, bring the liquid to a boil and simmer for 15 minutes. Remove the potatoes from the pot and reserve the cooking liquid.
Sauté onion in butter until transparent. Add the flour and sauté for 2 - 3 minutes. Add the cooking liquid and simmer for another 2 - 3 minutes. Add the clams and the potatoes. Season to taste.
Place the clam-and-potato mixture in a pie shell and cover with a second crust. Bake at 400◦F (200◦C) until the crust is golden brown.
Variation: Pâté aux palourdes ou grosses coques (Quahog Pie): Use the same method as above but do not cook the quahogs before adding them to the sauce. Simply open the quahogs with a knife, cut the flesh into pieces and add them to the pie with the potatoes. Pâté aux moules (Mussel Pie) may be made using the same procedure.
Steamed Clams (coques à la vapeur) - One of the most popular ways of preparing fresh clams is to steam them. To prepare the clams in the traditional way, wash them with sea water, if possible. If there appears to be a lot of sand in them, soak the clams in salt water for a couple of hours. Put the clams in a large pot without water and cover. Heat at medium heat for about 15 minutes or until all the clams are open. Serve the clams in soup bowls with the juice extracted during cooking. To eat the clams, take them from their shells, removing the brown membrane covering the neck. Dip the clams in the juice and eat them with bread and butter.