01 - Preheat grill to medium-high heat or oven to 425°F.
02 - Lay out four large sheets of heavy-duty aluminum foil, each approximately 16 inches long.
03 - In a large mixing bowl, toss baby Yukon gold potatoes with 1 tablespoon melted butter, kosher salt, and black pepper. Microwave potatoes for 3 minutes to begin softening.
04 - Divide par-cooked potatoes, corn pieces, cherry tomatoes, red onion, littleneck clams, and shrimp evenly among the foil sheets.
05 - Sprinkle each portion with minced garlic, Old Bay seasoning, and chopped parsley. Top with lemon slices. Drizzle each packet with the remaining melted butter and about 2 tablespoons of white wine or chicken broth.
06 - Fold the foil over the ingredients and tightly crimp the edges to seal the contents within each packet.
07 - Place the sealed packets on the preheated grill or onto a baking sheet in the oven. Cook for 20 to 25 minutes, until clams have opened, shrimp are opaque, and potatoes are fork-tender.
08 - Carefully open each packet, being cautious of escaping steam. Discard any clams that have not opened. Garnish with extra chopped parsley and serve with additional lemon wedges if desired.