Instructions

1. Fit a fine-mesh strainer over a medium heatproof bowl, preferably metal.
2. Place 1 (14-ounce) can sweetened condensed milk, 2 large egg yolks, and 1 tablespoon cornstarch in a small heavy-bottom saucepan and whisk to combine. While whisking constantly, bring to a boil over medium-high heat, occasionally scraping down the sides of the saucepan with a heatproof flexible spatula.
3. Continue boiling and whisking until thickened to the texture of pudding, about 1 minute more. Scrape the mixture into the strainer and press through the strainer with the flexible spatula, making sure to also scrape the underside of the strainer. Press a sheet of plastic wrap directly onto the surface of the pudding. Refrigerate until at least room temperature, 40 to 60 minutes. Meanwhile, make the crust.
4. Set aside 10 Nilla wafers from an 11-ounce package for decorating the top of the cheesecake. Place the remaining Nilla wafers (about 3 1/3 cups or 72 cookies) in a food processor fitted with the blade attachment. Process until finely ground, about 20 seconds. Transfer 1/4 cup to a small bowl and reserve for sprinkling.
5. Melt 1 stick unsalted butter in the microwave or on the stovetop. Add the butter and 1/2 teaspoon of the kosher salt to the remaining crumbs in the food processor. Process until combined, about 10 seconds. Transfer the mixture to a 9-inch springform cake pan. Press the crumbs evenly into the bottom and 1 inch up the sides. Refrigerate or freeze for at least 30 minutes to firm up.
6. Meanwhile, place 1 tablespoon water and 1 tablespoon vanilla extract in a small microwave-safe bowl and sprinkle 2 teaspoons powdered gelatin over the top. Set aside for at least 5 minutes to fully bloom. Juice 1/2 medium lemon until you have 1 tablespoon. Wipe the food processor bowl clean.
7. Transfer the cooled pudding to the food processor. Add 2 cups of the cold heavy cream, 8 ounces cream cheese, 8 ounces mascarpone cheese, and the remaining 1/2 teaspoon kosher salt. Process until smooth, about 1 minute.
8. Microwave the gelatin mixture until the gelatin is melted and the mixture is the consistency of warm corn syrup, about 15 seconds. Turn the food processor on, and immediately pour the gelatin mixture through the feed tube while still warm. Continue blending until smooth and creamy, 1 to 2 minutes.
9. Transfer half of the batter into the crust and spread it into an even layer with an offset spatula. Peel and thinly slice 2 1/2 large ripe bananas crosswise (about 1/8-inch thick). Arrange the slices evenly on top of the filling in a circular pattern. Brush the lemon juice onto the bananas.
10. Sprinkle the reserved 1/4 cup cookie crumbs evenly over the bananas. Top with the remaining batter and spread into an even layer. Cover with plastic wrap and refrigerate until set, at least 12 hours and up to 24 hours.
11. When ready to serve, place the remaining 1 cup cold heavy cream and 2 tablespoons powdered sugar in the bowl of a stand mixer (or large bowl if using an electric hand mixer). Beat with the whisk attachment on medium-high speed until thick and fluffy, 2 to 3 minutes. Transfer onto the cheesecake and spread into an even layer.
12. Peel and thinly slice the remaining 1/2 large ripe banana crosswise. Arrange the slices around the top edge of the cheesecake, overlapping and alternating them with the reserved whole Nilla wafers. Remove the sides of the springform pan before slicing.