1) Preheat the oven to 180C/Gas 4.
2) Scrub the clams under cold running water. Pry them open and rinse out any sand or grit. Gently separate the top and bottom shells, loosening and allowing the clam to divide, with some remaining on the top shell and some remaining on the bottom shell.
3) Use a knife to loosen the clam in the shell, removing any sand or grit that may have been under the clam. All of the clams may not divide evenly between the top and bottom shell. Cut these clams into small pieces and distribute among the other shells. You should have at least 16 clamshell halves to fill and bake.
4) Arrange the clam-filled shells on a baking sheet and set aside.
6) In a small bowl, toss together the bread crumbs, parsley, and garlic. Use a fork to stir the olive oil into this mixture. It should be moist but not oily. Set aside.
7) Fill each clam with a portion of the topping mixture, spreading it evenly over the clam to the edge of the shell. The filling should be about 0.25cm thick.
8) Bake until the topping begins to brown slightly, about 5 mins. Remove from the oven and adjust oven temperature to grill. Place the clams under the grill and cook until golden brown, about 2 mins. Serve immediately.