Preheat the oven to 350°F (175°C).
In a bowl, combine graham cracker crumbs, sugar, and melted butter. Stir until well mixed.
Press the mixture into the bottom and sides of a 9-inch pie pan. Bake for 10-12 minutes, or until the crust is golden and set. Let it cool completely.
In a medium saucepan, whisk together heavy cream, milk, egg yolks, sugar, and cornstarch.
Cook over medium heat, whisking constantly, until the mixture thickens (about 5-7 minutes).
Remove from heat and stir in lemon juice, lemon zest, and butter. Stir until smooth.
Pour the filling into the cooled crust and smooth the top with a spatula.
Chill in the refrigerator for at least 4 hours, or until set.
In a mixing bowl, beat heavy cream, powdered sugar, and vanilla extract until soft peaks form.
Spread the whipped cream on top of the chilled lemon filling before serving.
Slice and enjoy your tangy, creamy, and refreshing Lemon Cream Pie!