Preheat the oven to 375°. In a small bowl, mix the first 4 ingredients. In a large bowl, whisk the eggs. Whisk in the pumpkin, evaporated milk, and the sugar-and-spice mixture. Chop semisweet chocolate; sprinkle on the bottom of the piecrust. Gently pour pie filling into the piecrust. Bake until just set in the center, about 1 hour. During the last 10 minutes of baking, place candied pecans decoratively around the top of the pie. Let cool completely on a wire rack. Serve with whipped cream, if using.
The Do's and Don'ts of Cooking with Chocolate