Preheat oven to 350°F (175°C). Use 2 tablespoons melted butter to grease a 9x13 baking dish. Set aside. Like a baking sheet with aluminum foil. Set aside.
Bring a large pot of salted water to a boil. Add 1 pound of whole wheat spaghetti and cook according to package directions but reducing the cooking time by 2 minutes. Reserve 1 cup of pasta water before draining.
Load 10 to 12 Ritz crackers into a plastic zipper bag and lightly crush. Empty bag into a small bowl and add remaining melted butter to the crackers and stir to coat. Set aside.
In a large mixing bowl, stir together the 4 tablespoons softened butter, turkey, cream of chicken soup, sour cream, sherry, garlic powder, parsley, sea salt, nutmeg, and pepper. Whisk in 1 cup of turkey stock until smooth.
Fold the cooked spaghetti into the turkey mixture. Stir to coat. Add reserved pasta water gradually to achieve a gravy-like consistency or slightly thinner. You may or may not require all of the pasta water.
Spread the mixture evenly in the prepared baking dish. Put the casserole dish on a foil-lined baking sheet in the event of bubble over.
Add mozzarella halves over the pasta, lightly pressing into the sauce. Grate Parmesan cheese directly over the dish. Top with the buttered cracker mix and bake, uncovered, for 40-45 minutes until bubbly and golden brown. Let it stand for 5 minutes after removing from the oven. Serve hot with additional Parmesan cheese if desired.