Preheat your oven to 350 degrees. This ensures that your crust bakes evenly and crisps up perfectly.
In a medium bowl, combine graham cracker crumbs, gingersnap crumbs, and butter. Mix until well combined. You want a texture similar to wet sand. This will be your crust.
Press the crumb mixture into the bottom of a 9×13-inch baking pan. Use the back of a measuring cup to compact it firmly. This step is crucial as it creates a sturdy base for your bars.
Place the pan in the oven and bake for about 10 minutes, until golden brown. You’ll want to keep an eye on it to avoid over-browning. Once done, remove it from the oven and set the pan on a wire rack to cool.
In a medium saucepan, combine 2 ¾ cups milk, banana puree, ¾ cup sugar, and vanilla. Cook over medium heat, whisking frequently until the mixture boils. It’s important to stir to prevent sticking and ensure a smooth mixture.
As soon as it boils, remove the pan from the heat and set it aside to cool slightly. This mixture will become the creamy filling of your bars.
In a small bowl, combine ¼ cup milk and gelatin. Let it sit for about 5 minutes to soften the gelatin. This step is essential for achieving the right consistency.
While the gelatin softens, whisk together egg yolks, remaining ¼ cup sugar, and flour in a separate bowl until smooth. This mixture will help thicken your pudding.
Once the gelatin has softened, add it to the milk and banana mixture, whisking well to combine. It’s important to incorporate it fully for an even texture.
Ladle about 1 cup of the hot milk mixture into the yolk mixture, whisking constantly to combine. This step gradually raises the temperature of the eggs, preventing curdling. Pour the yolk mixture back into the milk mixture, whisking continuously.
Cook this mixture over medium-high heat, stirring constantly. Keep an eye on it as it thickens. You’ll want it to boil gently for about 2 minutes.
Remove from heat and strain the filling through a wire-mesh sieve into a bowl. This step is crucial for achieving a silky-smooth filling. I find it helpful to use the back of a spoon to push it through, although it can be a bit tedious.
Spread half of the filling onto your cooled crust. Layer with mini vanilla wafers, then cover with the remaining filling. This layering creates a beautiful and delicious cross-section.
Let the bars cool to room temperature, then refrigerate for at least 6 hours. Patience is key here; the chilling time helps the bars set properly.
Finally, in a medium bowl, combine heavy whipping cream and confectioners’ sugar. Beat at medium speed with an electric mixer until medium peaks form. This fluffy topping will be the crowning glory of your bars. Spread it evenly on top of the cooled filling.
Cut into squares to serve and garnish with additional mini vanilla wafers if desired. These bars can be stored in the refrigerator for up to 5 days, but I doubt they’ll last that long!