How to Make It
Place clams in a large bowl; add ice cubes and 1/4 cup salt. Add just enough cold water to cover clams by 1 inch. Let clams purge 30 minutes.
Meanwhile, preheat oven to 550°F with oven rack about 6 inches from heat. Mash butter, garlic, shallot, parsley, wine, pepper, and remaining 1/4 teaspoon salt in a small bowl with a fork until mixture is smooth. Set garlic butter aside.
Lift clams from bowl, shake dry, and place, hinge sides down, in the wells of 4 (6-well) escargot trays (or place clams on their sides on an aluminum foil–lined rimmed baking sheet). Roast in preheated oven until clams just begin to open, 4 to 5 minutes. Taking care not to jostle trays or baking sheet and spill clam juice, remove clams from oven. Increase oven temperature to broil on high. Spoon about 1/2 teaspoon garlic butter into each clam shell, and return to oven. Broil until clams completely pop open and butter is bubbling, about 6 minutes. (Discard any clams that do not open.) Remove clams from oven, and serve immediately with crusty bread.