To make the Cookie Crust: Preheat the oven to 350 degrees F. In a medium bowl, add the cookie crumbs and salt. Pour the melted butter on top and mix with your hands until the butter is evenly distributed. It should feel like wet sand. Add the mixture to a 9-inch pie dish and press it onto the bottom and up the sides of the dish until it’s one even layer. Transfer to the oven to bake for 10 minutes, until the bottoms and edges have set. Remove and allow to cool completely before filling.

To make the Espresso Cream: Place a sieve or strainer over a bowl and set aside. In a medium skillet, whisk together sugar, cornstarch, salt and 1/4 cup milk together until the corn starch has dissolved.. Turn the heat to medium and then pour in the remaining 2 1/4 cups milk. Whisk until completely combined. While the milk is heating up, add the espresso powder and whisk until dissolved. Bring the entire mixture to a slight boil and then cook for 2 to 3 minutes, until thickened, stirring the entire time. In a separate bowl, whisk the egg yolks; add a few tablespoons of the hot mixture to the eggs to temper them and then pour the egg mixture into the milk mixture. Bring it to a simmer, cooking for the custard for about 3 to 3 minutes, stirring the entire time, until thickened. Pour the espresso cream through the strainer into the bowl, catching any eggy bits. Immediately whisk in the rum and vanilla extract.

Pour the espresso cream into the prepared pie cookie crust and smooth out the surface with a spatula. Immediately place a sheet of plastic wrap onto the surface of the custard. Allow to come to cool slightly on your kitchen counter for 10 minutes and then transfer to the fridge to chill for at least 3 hours, ideally overnight.

To make the mascarpone cream: add the mascarpone, sugar, egg yolk and heavy cream to the bowl of stand-up mixer with the paddle attachment and beat until smooth. Transfer to a piping bag and pipe onto the top of the pie however you like. You can also spoon it on and smooth it out with a spatula.

Dust the topping with cocoa powder and slice it up and serve.