Preheat oven to 375 degrees. Make the crust by tossing together crushed graham crackers and melted butter in a small mixing bowl. Press into the bottom of a standard pie plate (not deep dish). Bake in the preheated oven for 7 minutes.
Meanwhile, make the fudgy cake layer. Place chocolate chips and butter into a microwave safe mixing bowl. Microwave for 30 seconds at a time, stirring in between, until everything is melted and smooth.
Pour in sugar, cocoa powder, flour, espresso powder (if using), eggs, and vanilla extract. Use a hand mixer to beat together until just combined. Do not over mix. Scrape the sides and bottom of the bowl to ensure everything is mixed in. Pour into the baked chocolate graham cracker crust.
In a medium bowl, prepare the streusel topping by stirring together brown sugar, flour, and cocoa powder. Use a pastry blender (or two knives) to cut the butter into the flour mixture until it resembles small pebbles. Add in roughly chopped graham crackers and toss to combine.
Sprinkle streusel evenly over the top of the fudgy cake layer. Return pie to the oven and bake 25 to 30 minutes at 375 degrees Fahrenheit.
While pie is baking, make the ganache by placing chocolate chips into a mixing bowl. Heat heavy cream in the microwave until simmering, about 45 seconds. Pour hot cream over chocolate chips. Let stand 2 minutes, then stir until smooth.
Drizzle ganache over the fully baked pie. Let cool for 15 minutes before serving, or cool completely.