Preheat the oven to 375°. In a small bowl, mix the first 6 ingredients. In a large bowl, whisk the eggs. Whisk in the pumpkin, evaporated milk, and the sugar-and-spice mixture; pour into the piecrust. Bake until just set in the center, about 1 hour. Immediately after baking, top the pie with meringue cookies. Let cool completely on a wire rack. Serve with whipped cream, if using.