Preheat oven to 375F. Place prepared pie crust in pie plate. In a large bowl, beat eggs with a fork. Stir in pumpkin, half-and-half, and maple extract. Stir in sugar, flour, lemon peel, vanilla, salt, cinnamon, nutmeg, and allspice. Pour pumpkin mixture into pastry-lined pie plate. Cover edge of the pie with foil to prevent overbrowning. Bake for 35 minutes.

Meanwhile, in a small bowl, stir together nuts and butter. Remove foil from pie. Sprinkle nuts over the top of the pie, leaving about a 1-inch border around the edge.

Bake about 10 minutes more or until a knife inserted near the center comes out clean (push nuts to the side to check doneness, then push nuts back into place). Cool on a wire rack. Cover and refrigerate within 2 hours. Drizzle with maple syrup just before serving.

To Bake Ahead: Prepare and bake pie as directed. Cool on a wire rack for 1-1/2 hours. Cover lightly with plastic wrap. Store in the refrigerator for up to 2 days. Drizzle with syrup just before serving. Makes 8 servings.