In a medium size pot over medium heat warm the milk and the vanilla bean just until boiling. Just as it reaches a boil, remove it from the heat and let it cool slightly.
In the bowl of an electric mixer fitted with the paddle attachment, beat the egg yolks and the sugar on medium speed until it becomes pale and thick. Reduce the mixer to low and stir in the flour and cornstarch, stopping the mixer to scrape down the sides periodically. Remove the vanilla bean from the milk, and slowly stir the milk into the egg/flour mixture.
Pour this mixture back into your pot and heat gently over a medium heat. Using a wire whisk (if you don’t have one, a wooden spoon will work also), continuously whisk the mixture until it thickens and comes to a boil. Boil for one minute and keep on whisking so that lumps do not form and the mixture doesn’t stick to the bottom of the pot. Remove from the heat and continue to whisk for a minute or two then pour the mixture into a large bowl to cool. Cover the surface of the mixture with plastic wrap so that a skin doesn’t form.
You can make this pastry cream a day in advance and keep it covered in the refrigerator.
When you’re ready to use the pastry cream, take the ripe banana and with a fork or the back of a spoon, mash the banana until it’s almost like a puree. Then whisk it into the pastry cream. If you choose to use the coconut, whisk it into the pastry cream.
Place the graham crackers and almonds in a food processor and pulse until you have fine crumbs, transfer to bowl and set aside.
In a medium bowl beat (either with a stand mixer with whisk attachment, hand mixer or wire whisk) the heavy cream and powdered sugar until stiff peaks form. You can make the whipped cream in advance too, just cover and keep in the fridge a day in advance.
To assemble the shooters: Place two teaspoons of the crumbs into the bottom of the shot glass. Slice the remaining banana into 1/2? slices, and place the banana on top of the crumbs. You can spoon the pastry cream into the shot glass or you can pipe it in with a pastry bag. Using a pastry bag fitted with a star tip, pipe the whipped cream on top of the pastry cream layer. Garnish with sliced almonds, sliced bananas or toasted coconut.