Make the pie dough: In a medium bowl, mix 1 1/2 cups all-purpose flour and 1/2 teaspoon salt. Cut in 1/2 cup cold unsalted butter (cubed) using a pastry cutter or your fingertips until the mixture looks like coarse breadcrumbs with pea-sized butter pieces visible throughout. This takes about 3–5 minutes. Checkpoint: You should see small lumps of butter throughout, not a smooth paste.

Add water gradually: Drizzle 4 to 6 tablespoons of ice water over the flour mixture (start with 4 tablespoons). Stir with a fork after each addition until the dough just begins to clump together. Do not overmix. This takes about 2 minutes. Checkpoint: The dough should hold together when squeezed but not feel wet or sticky.

Chill the dough: Shape the dough into a flat disk about 1 inch thick using plastic wrap (this keeps your hands clean). Wrap tightly in plastic wrap and refrigerate for at least 1 hour at 35–40°F. You can also freeze this for up to 1 month. If frozen, let thaw in the refrigerator for 30 minutes before rolling.

Preheat and prepare: Remove dough from refrigerator 10 minutes before rolling. Preheat oven to 375°F. Lightly dust a clean countertop and rolling pin with flour.

Roll out the dough: Place dough disk on the floured surface. Using a rolling pin, roll from the center outward, rotating the dough 45 degrees every 2–3 rolls. Continue until the dough is a thin circle about 11–12 inches in diameter and about 1/8 inch thick. This takes about 5–8 minutes. Checkpoint: The dough should stretch easily without tearing. If it cracks at the edges, pinch it back together.

Transfer to pie pan: Loosely roll the dough around the rolling pin and carefully unroll it over a 9-inch pie pan, centering it so equal overhang exists on all sides (about 1 inch). Let the dough settle naturally into the pan without stretching.

Trim and crimp edges: Using kitchen shears or a sharp knife, trim the dough to 1.5 inches beyond the rim of the pan. Fold the overhang under itself (creating a raised edge) and crimp decoratively using your thumb and forefinger, pressing at 1-inch intervals around the circumference. This takes about 2 minutes.

Prick and chill crust: Using a fork, gently prick the bottom and sides of the crust all over (about 20–25 pricks total). This prevents puffing and air bubbles. Place the crust in the refrigerator for 30 minutes at 35–40°F. The crust should feel very cold and firm to the touch.

Blind bake (pre-bake): Line the chilled crust with parchment paper or a coffee filter, then fill with pie weights, dried beans, or rice (about 2 cups). Bake at 375°F for 15 minutes on the center rack. The edges should begin to set and lighten. Checkpoint: The edges should look dry and pale, not dark brown.

Remove weights and finish baking: Carefully remove the parchment and weights (set aside to cool). Return the crust to the oven and bake for another 8–12 minutes until the bottom is light golden and dry to the touch (not wet-looking). The crust should look pale to light golden throughout, not brown. Remove and let cool on a wire rack for at least 15 minutes while you prepare the filling.

Make the custard filling: Pour 2 cups whole milk into a medium saucepan. Place on medium heat and bring to a gentle simmer (small bubbles forming around the edges), about 5–7 minutes. You should see gentle steam rising but the milk should not boil vigorously. Checkpoint: The milk should be too hot to touch comfortably (around 170–180°F if using a thermometer).

Prepare the thickening mixture: In a separate medium bowl, whisk together 1/2 cup granulated sugar, 1/4 cup cornstarch, and 1/4 teaspoon salt until no lumps remain, about 1 minute. Press any lumps against the side of the bowl with the back of a spoon.

Prepare egg yolks: In another medium bowl, whisk 4 egg yolks until combined and slightly lighter in color, about 1 minute. Do not overbeat or they will become too frothy.

Temper the eggs (this prevents scrambling): Slowly pour the hot milk into the egg yolks while whisking constantly. Pour in a thin stream over 2–3 minutes while whisking vigorously without stopping. This gradual addition allows the eggs to warm up safely. Checkpoint: The mixture should be hot to the touch and a pale yellow color without any cooked egg white visible.

Return to heat and thicken: Pour the entire tempered egg-milk mixture back into the saucepan (scraping the bowl) and return to medium heat. Whisk constantly and scrape the bottom and corners with a whisk or wooden spoon to prevent lumps and scorching. Cook for 2–3 minutes until the mixture thickens visibly and you see 2–3 slow bubbles breaking the surface in the center of the pan. Checkpoint: The mixture should coat the back of a spoon; if you draw your finger across the spoon, it should leave a trail that doesn't immediately fill in.

Finish the custard: Remove from heat immediately. Stir in 2 tablespoons unsalted butter and 2 teaspoons vanilla extract, stirring until the butter melts completely and the mixture is smooth, about 1 minute. The custard should be glossy and silky.

Cool the custard: Pour the hot custard into a medium bowl. To prevent a skin from forming, press plastic wrap directly onto the surface of the custard (the plastic should touch the custard, not hover above it). Refrigerate for at least 2 hours at 35–40°F, or up to 24 hours. The custard should be completely cold before assembling.

Prepare bananas: Remove bananas from the refrigerator 30 minutes before assembly. Peel and slice 3 to 4 ripe but firm bananas (about 1/4 inch thick slices) into a small bowl. Immediately toss with 2 tablespoons fresh lemon juice and stir gently to coat all surfaces. The lemon juice prevents browning. Use immediately; do not let bananas sit longer than 5 minutes.

Assemble the pie: Remove the cooled pie crust from the pan and place on a serving plate or pie server. Spread a thin layer (about 1/4 inch) of chilled custard on the bottom of the crust, covering the entire surface, about 2–3 minutes. This layer acts as a sealant to keep the crust from getting soggy.

Add banana layer: Arrange the lemon-coated banana slices in a single, slightly overlapping layer on top of the thin custard base. Work quickly to prevent browning. This should take about 2 minutes. Checkpoint: All bananas should be completely covered with lemon juice and arranged evenly.

Top with remaining custard: Spread or gently pour the remaining chilled custard over the banana layer, using a spatula to create an even, smooth surface. Make sure the custard fills in around the bananas and reaches the crust edges to seal them. This takes about 2 minutes. Checkpoint: The custard should be level and no banana slices should be peeking through the top.

Make whipped cream topping: Pour 1 1/2 cups heavy whipping cream (cold from the refrigerator) into a chilled medium bowl. Using an electric mixer on medium-high speed (or a whisk if mixing by hand), whip the cream for about 1–2 minutes until soft peaks form (cream holds a shape but tips curl over when the beater is lifted). Add 3 tablespoons powdered sugar, 1/2 teaspoon vanilla extract, and a tiny pinch of salt. Continue whipping for another 30–60 seconds until stiff peaks form (cream holds a sharp point when the beater is lifted). Do not overwhip or the cream will become grainy and butter-like.

Top the pie: Using a spatula or spoon, mound or spread the whipped cream generously over the custard layer, creating peaks and swirls as desired. Work quickly as whipped cream can soften if handled too long. Garnish with optional toppings: thin banana slices, chocolate shavings, or a light dusting of nutmeg.

Chill before serving: Refrigerate the finished pie for at least 30 minutes (up to 4 hours) before serving. This allows the pie to set slightly and the flavors to meld. The pie should feel cold to the touch and the custard should hold its shape when sliced.

Slice and serve: Using a sharp knife dipped in hot water and wiped clean between cuts, slice the pie into 6 or 8 equal portions. A hot knife creates cleaner edges and prevents the custard from dragging. Serve immediately on chilled plates if possible. Each slice should show distinct layers: golden crust, creamy custard, banana pieces, and fluffy whipped cream on top.