Layer graham cracker squares onto a baking sheet lined with parchment paper. Generously spoon ~1/4 cup vanilla pudding onto each graham cracker. Add 2-3 banana slices on top of the pudding. Spoon a little more vanilla pudding on top of the banana slices (this will act like a glue) and top with another graham cracker square. Freeze for at least 2 hours. Dust with powdered sugar before eating :)