If making homemade graham cracker crust, make it and chill it until ready to fill.: When you press the crumb mixture into the pan you should hear a faint crunch and feel the crust compact under your fingers, which signals it will hold the filling. Chilling solidifies the butter so the crust stays intact, and failing to press firmly enough is the most common mistake, which leads to a crumbly base when slicing. If your crust seems loose, press again and chill longer, the extra rest time improves structure and mouthfeel.
Whisk pudding mix and milk and let set 5 minutes.: As you whisk the pudding mix into the milk you will notice the liquid transform from glossy to a thicker, opaque cream, with a faint vanilla aroma rising. Letting it sit allows the starches to hydrate and the mixture to take on the right body; rushing this step can leave a runny filling, so give it the full five minutes for consistent texture. If lumps appear, a quick whisk or brief strain through a mesh will smooth it out.
Add peanut butter and stir until smooth and thick.: When you add the room temperature peanut butter the mixture will deepen in color and begin to smell nutty and warm, even though it is cool to the touch. Stir until the blend is glossy and thick, which indicates the fats and dairy are fully combined. A common slip is using cold peanut butter, which can create streaks and make blending difficult, so warm the jar slightly if needed for an even, creamy result.
Add half the cool whip to the peanut butter mixture and carefully fold in until it’s combined.: Folding in the reserved Cool Whip introduces air and lightens the pudding, creating a soft, cloudlike texture you can see as gentle ribbons vanish into the mixture. Use a wide spatula and scoop from the bottom, turning the bowl to avoid deflating the foam; overmixing will collapse the air and yield a denser filling, which is the main mistake to avoid. Stop when the color and texture look uniform and airy.
Slice 1 banana and place in the bottom of prepared pie crust, slicing more as needed to cover (about 1 1/2 bananas depending on size).: As you slice the banana you will notice a sweet aroma and a soft, yielding flesh that layers beautifully over the crust. Arrange the slices in a single even layer so the filling sits flush and every bite includes fruit. Slicing too thin can lead to quick browning and a mushy feel, so aim for medium thickness for the best balance of texture and appearance.
Cover the bananas with the pudding mixture. Cover and chill until set, at least 2 hours before serving.: When you spoon the filling over the bananas it should flow like a dense ribbon and settle around the fruit, creating an even top. Chilling allows the pudding to firm up and meld with the banana layer, delivering clean slices when served, and the typical error is not chilling long enough which results in a soupy center. Aim for at least two hours, though longer chilling improves slicing and flavor melding.
Before serving: top with remaining whipped topping. Place about 1/4 cup peanut butter in a small bowl and heat in the microwave for about 10-20 seconds until it’s thin enough to spread. Add to a plastic baggie and cut off one tip; pipe over whipped topping. Garnish with additional sliced bananas.: The aroma of warmed peanut butter is instantly enticing, and when drizzled over the pale whipped topping it creates a striking visual and taste contrast. Use a gentle hand while piping to form delicate ribbons and add fresh banana slices for brightness. Avoid overheating the peanut butter ; if it becomes too thin it will run off the pie, and if too cool it will not drizzle smoothly, so heat in short bursts and test the viscosity.
Store in the refrigerator, covered, for up to 2 days.: In the fridge the pie will be cool to the touch and maintain its layers, but moisture can form on the surface if left uncovered, which dulls texture and presentation. Covering protects the top and preserves freshness, and over time the bananas will slowly brown, which is the primary change to expect. Consume within two days for the best flavor and appearance, and avoid freezing which can ruin the creaminess and make the bananas mushy.