Place 2 c white wine, 1 1/2 cup sliced shallots, 2 tbsp chopped garlic, 1/2 cup parsley, and 3 sprigs thyme in a pot and bring to boil. Add 3 dozen clams in one layer and cover. Shake occasionally while they cook. Remove clams as they open and place into a bowl. Discard any unopened clams. Allow clams to cool before removing them from their shells. Save 36 shell halves for stuffing.In a bowl, mix 11 oz softened butter, 2 tbsp diced prosciutto or Serrano ham, 2 tsp minced shallots, 2 tsp minced garlic, 3 tbsp chopped parsley, 1/4 c panko, and salt and pepper. Place a cooked clam in each half shell and cover with a tsp dollop of the butter mixture. Place on a sheet pan and top with some additional panko. Heat the broiler and broil clams until topping is golden brown. Serve immediately.
