This dish is a traditional specialty of the East End of the Hamptons. The clams may be steamed open (briefly) instead of shucked. (Steaming is easier.)
FOR THE PIECRUST:
- 2 cups flour
- 1⁄2 tsp. salt
- 1⁄4 tsp. baking powder
- 8 tbsp. chilled butter, cut into small pieces
- 2 tbsp. chilled vegetable shortening, cut into small pieces
FOR THE FILLING:
- 3 medium russet potatoes, peeled and quartered
- 2 cups clam juice
- 5 strips bacon, cut into 1/2" pieces
- 1 medium yellow onion, peeled and finely chopped
- 1⁄4 cup chopped fresh parsley leaves
- 1 tbsp. fresh thyme leaves
- 3 cups shucked steamer or cherrystone clams, roughly chopped
- 2 tbsp. flour
- Salt and freshly ground black pepper
- 2 tbsp. chilled butter, cut into small pieces
For the piecrust: Mix together flour, salt, and baking powder in a medium bowl. Quickly work butter and shortening into flour mixture with the tips of your fingers until mixture resembles coarse meal. Sprinkle with 8 tbsp. ice water and stir with a fork until just combined. Form into a ball, then flatten into a disk and divide in half. Cover with plastic wrap and refrigerate for at least 30 minutes.
For the filling: Boil potatoes in clam juice in a covered pot over medium heat until soft, about 30 minutes. Drain, lightly mash with a fork, and set aside.
Meanwhile, saute bacon in a skillet over medium-low heat until crisp, about 7 minutes. Transfer bacon to a paper towel. Add onions to bacon fat and saute until golden, about 15 minutes. Mix together bacon, onions, parsley, thyme, clams, flour, and potatoes in a bowl. Season with salt and pepper to taste.
Preheat oven to 400°. Roll out dough on a lightly floured surface into two 12" circles. Fit 1 circle into a 9" deep-dish pie pan. Add clam filling, mounding it in the center. Top with butter. Lay remaining dough over filling. Trim dough, leaving about 1" around edge; fold under and crimp two layers together. Make a little hole in center of pie to allow steam to escape. Bake until golden, 50-55 minutes.