Start by chilling a mixing bowl and sifting together the all-purpose flour, granulated sugar, and salt. Cut cold unsalted butter into the flour mixture with a pastry cutter until it resembles coarse sand. Gradually add 4-5 tablespoons of ice-cold water mixed with 1 tablespoon of apple cider vinegar until the dough comes together. Shape it into a disc, wrap in plastic, and refrigerate for at least 2 hours.

Once chilled, preheat your oven to 375°F (190°C). Roll out the dough on a floured surface to fit your pie dish, then transfer it carefully into the dish. To prevent bubbling, use parchment paper and weights, then blind bake for 20 minutes until golden. Remove from the oven and let it cool completely before filling.

In a medium bowl, whisk together 4 egg yolks and 1/2 cup of granulated sugar until pale and creamy. Meanwhile, heat 2 cups of whole milk in a saucepan until just simmering. Gradually temper the egg mixture by adding a splash of the hot milk. Return the mixture to the saucepan and cook over medium heat, whisking constantly until thickened, about 5 minutes. Stir in 2 tablespoons of unsalted butter until melted, then remove from heat and let cool.

In the cooled pie crust, layer 2-3 sliced bananas evenly at the bottom. Pour the rich and silky pastry cream over the banana slices, using a spatula to smooth the top. Cover with plastic wrap to avoid skin formation and refrigerate for 3-4 hours until set and firm to the touch.

In a large mixing bowl, combine 1 cup of heavy cream, 1/2 cup of mascarpone, and 2 tablespoons of powdered sugar. Using an electric mixer, whip the mixture on medium-high speed until stiff peaks form, taking care not to overwhip. Once the pie has set, spread the Chantilly cream generously on top just before serving, and garnish with lemon-juiced banana slices to prevent browning.