First, make the dulce de leche. This recipe makes it from scratch by baking sweetened condensed milk, but if you have pre-made dulce de leche - move on to step 2! Preheat the oven to 425° Fahrenheit. Pour the contents of one 14 oz can of sweetened condensed milk into a glass pan (I use a pie pan) then cover the pan with tin foil. Next, set the pan into another, larger, baking or roasting pan (or large oven-safe frying pan) and fill that pan with at least 1.5 inches of water (essentially you're making a bain-marie). Place the entire bain-marie into the oven and bake for 2 to 2 and a half hours (it seems like a long time but it's worth the wait!). Check every hour to be sure there is still water in the larger pan (or the dulce de leche will burn. Once it's done it will be a deep caramel color. Remove from oven and let cool. Once it's cool, scoop dulce de leche into a container and stir in the salt, then set aside.
Next, make the cupcakes! Preheat the oven to 350° Fahrenheit and line two cupcake trays with paper liners then set aside. Crush the graham crackers and then toss in a medium bowl. Mix together with the melted butter (should look like wet sand but not be liquidy). Add in the salt and ground ginger and mix. Then, spoon about one tablespoon of the mixture into the bottom of each paper cupcake liner and press down until flat. Then set aside.
In a large mixing bowl, mash the four bananas until totally goopy and no large chunks remain. Add in the melted salted butter, sour cream, eggs, vanilla, and sugar and whisk together until creamy and lighter. Add in the flour, baking powder, and salt and stir to combine. Then scoop batter into the graham-cracker-crust lined cupcake pans - each cup should be about 3/4 full. Bake for 18-20 minutes or until the top of a cupcake springs back with touched. Let cupcakes cool before filling and topping them.
While the cupcakes are cooling, make the stabilized whipped cream! In a small saucepan, combine the powdered gelatin and cold water and mix to combine - it should thicken up instantly a bit. Then, heat over low heat, stirring constantly, until all gelatin dissolves. Turn off heat and pour the mixture into a cup or small bowl to cool (but not set!). While the gelatin is cooling, start beating the heavy cream on high with an electric mixer until it becomes thicker but before soft peaks form. Add in the powdered sugar and continue to beat for a few seconds, then slowly pour in the cooled gelatin liquid and continue to beat until stiff peaks form. Then scoop into a piping bag.
Once the cupcakes are cool, use a small paring knife to cut a 1x1 inch square into the top of each cupcake and remove the chunk (and eat it for a snack). Fill each hole with about a teaspoon or more of the dulce de leche. Then, pipe the stabilized whipped cream on top of the cupcake, covering up the dulce de leche.
Last step! Place your dark chocolate baking bar on a cutting board, and, using a large knife or a hand-held vegetable peeler, scrape the bar so that chocolate shavings form. Toss shavings on top of the whipped cream and serve!