Place a fine-mesh sieve over a medium bowl.

In a medium saucepan, heat milk over medium heat until steaming. (Do not boil.)

In a medium bowl, whisk together sugar, cornstarch, eggs, egg yolks, flour, vanilla bean paste, and salt. Gradually whisk hot milk into sugar mixture. Return mixture to saucepan, and cook over medium heat, whisking constantly, until bubbly and very thick, 4 to 6 minutes. Strain through prepared sieve. Cover with a piece of plastic wrap, pressing wrap directly onto surface of pudding to prevent a skin from forming. Let cool completely.

Transfer 2 cups (510 grams) pudding to another medium bowl; whisk in chocolate-hazelnut spread until smooth.

In the bottom of a 9-inch square baking dish, place banana slices and Vanilla Wafers in a single layer, alternating between the two. Spoon chocolate-hazelnut pudding on top, smoothing with an offset spatula. Place banana slices and wafers in a single layer, alternating between the two, on top of pudding. Spoon vanilla pudding on top, smoothing with an offset spatula. Place bananas and Vanilla Wafers in a single layer, alternating between the two in a checkerboard-like pattern. Cover and refrigerate for 3 hours or up to overnight. Before serving, spoon Swiss Meringue on top, spreading as desired with an offset spatula. Using a handheld kitchen torch, lightly brown meringue. Decorate with remaining Vanilla Wafers and remaining banana slices. Serve immediately.