Split the mirlitons in half lengthwise. Put them in a kettle of cold water with salt to taste. Bring to the boil and let simmer about 10 minutes. Do not overcook or the mirlitons will become mushy. Drain and run briefly under cold water. Drain again.
Using a spoon or melon-ball cutter, scoop out the flesh and seeds of each half, leaving a shell about ⅛inch thick or slightly thicker. Set the shells aside. Chop the flesh and seeds fine. There should be about 1cup.
When ready to cook, preheat the oven to 425 degrees.
In a mixing bowl, combine the chopped pulp with 1cup bread crumbs, 2cups cheese, the egg, garlic, scallions, red pepper flakes, salt, and pepper.
Use this mixture to fill the mirliton halves. Pile the filling up and smooth it over.
Combine the remaining ½cup cheese with remaining ½cup bread crumbs. Sprinkle the tops with the mixture, patting to help it adhere. Dot the tops of each half with butter.
Arrange stuffed halves on a lightly buttered baking dish. Place in the oven and bake20 minutes.