Cook the clams. Scrub the shells of the clams under cool water. Discard any clams that are opened or with gaping shells. Fill a large pot of water ½ of the way with water - enough water to almost cover the clams completely so they all open at the same time. Add a small quartered onion, bay leaf, and peppercorn to the water or you can just cook the clams in plain water. Bring to a boil and add the clams. Cover and cook for 6 to 10 minutes, until the clams have opened and the meat has turned opaque. Remove the clams from the water, strain the broth and reserve up to 1 ½ cups broth. Let the clams cool for 10 to 15 minutes, remove the clam meat from the shells, and set aside. Separate the clamshells into two pieces, clean off any broken pieces or remaining residue. Reserve about 18-20 of the best shells.
Prepare the stuffing ingredients. In a food processor, pulse the crackers into a fine crumb. Set aside. Wipe out the food processor and repeat with the onion, celery, and red pepper. Pulse until the vegetables are minced but not puréed, set aside. Wipe out the food processor and repeat with the clams. Pulse the clams in the food processor just until the clams are chopped into small to medium pieces, set aside.
Make the stuffing. In a large skillet, melt the butter over medium-high heat. Add the onions, celery, and pepper, season with a sprinkle of salt and black pepper. Cook the vegetables until translucent, about 3 minutes, then remove from the heat. In a large bowl, combine the sauteed vegetables, chopped clams, and cracker crumbs (see notes.) Melt the remaining butter and pour over the mixture. Add the Worcestershire, lemon juice, garlic, ¼ teaspoon salt, ⅛ teaspoon pepper, and fresh parsley. Mix the clam broth into the stuffing a little at a time, until the stuffing mix is thick but a little wet. It should be similar to a thick paté.
Stuff the shells. Preheat the oven to 375°F. Stuff the clean shells with the mix, lightly pressing the stuffing into the clamshell. The stuffing should be slightly round on top. Set each stuffed shell on a lipped baking sheet. Optional: Top each stuffed clam with a 1-inch slice of bacon before cooking.
Bake the stuffed clams. Bake the clams for 45 to 50 minutes or until the top of the stuffed clams is rich brown in color, slightly crunchy and if using the bacon, the bacon should be crispy. Serve right away, plain, with lemon, or hot sauce.