Preheat the oven to 400 degrees . Fit the piecrust into a 9-inch pie pan; crimp the edges. Refrigerate for 15 minutes. Line the crust with foil and fill with pie weights or dried beans; bake for 15 minutes. Remove the foil and weights, reduce the oven temperature to 350 degrees and bake until the crust is golden, 9 to 14 minutes.
In a medium saucepan, whisk together the sugar, cornstarch and salt. Whisk in the egg, egg yolks, cream, milk and maple syrup. Cook over medium heat, whisking, until the mixture begins to boil and thickens, about 7 minutes. Remove from the heat and whisk in the butter.
Transfer 1 cup of the custard to a medium bowl and stir in the pumpkin. Pour the remaining custard into the crust; smooth the top. Spoon and spread the pumpkin mixture on top of the custard. Refrigerate the pie until set, at least 3 hours.