For the crust:Stir the butter, oil, sugar, and salt together in a medium bowl until evenly combined.
Add the measured flour and stir until a soft dough forms.
Heat the oven to 350°F and arrange a rack in the lower third.
Place a baking sheet on the rack while the oven is heating.
Place all of the ingredients except the whipped cream in a large bowl and whisk until smooth and combined.
Pour into the chilled pie crust.
Place the pie on the hot baking sheet and bake until the top starts to brown and the filling is set but still jiggles slightly in the center, about 50 minutes.
Remove from the oven to a wire rack and let cool completely before serving. Top slices of the pie with whipped cream, if desired.