1/2 Teaspoon Dried Dill Weed, Or To Taste (optional)
Preheat oven to 350 degrees F. Grease a 9×13 baking dish.
Bring a large pot of lightly salted water to a boil. Cook elbow macaroni in the boiling water, stirring occasionally until cooked through but firm to the bite, 8 minutes. Drain and return macaroni to pot.
Stir 1/4 cup butter, 1/4 cup milk, and 2 Cups of Cheddar into the cooked macaroni. Stir cream of mushroom soup, tuna, and 1/2 cup milk into the macaroni and cheese. Pour macaroni mixture into the prepared baking dish; top with Cheddar cheese and parsley.
Mix bread crumbs, melted butter, and dill in a small bowl; sprinkle remaining Cheddar cheese layer. Top with bread crumb mixture.
Bake in the preheated oven until cheese is melted and bread crumb topping is lightly browned, about 20 minutes.