Preheat your oven to 350°F (175°C). In a medium mixing bowl, combine graham cracker crumbs, granulated sugar, and melted butter until evenly moistened. Press the mixture firmly into the bottom and up the sides of a pie dish. Bake in the preheated oven for 8-10 minutes until golden and fragrant, then allow it to cool completely.

In a saucepan, whisk together granulated sugar, cornstarch, all-purpose flour, and a pinch of salt. Gradually add water while stirring to avoid lumps. Cook over medium heat, stirring continuously, until the mixture thickens and bubbles, about 5-7 minutes. Remove from heat, temper in the egg yolks, then stir in butter, lemon zest, and fresh lemon juice until smooth. Allow the filling to cool slightly before pouring it into the cooled crust.

In a large bowl, beat the softened cream cheese and powdered sugar together until creamy and well combined, about 2-3 minutes. Gently fold in the heavy whipping cream and vanilla extract, mixing until the cream layer is smooth and fluffy.

Once the lemon filling has cooled, spread the cream layer evenly over the lemon filling in the crust. Cover the pie with plastic wrap and refrigerate for at least 4 hours or overnight.

When ready to serve, slice the chilled Lemon Supreme Pie into wedges. Garnish with additional whipped cream and lemon slices.