Make a double batch of pastry cream using a double boiler or bain marie (glass bowl over a saucepan of simmering water). Add 1 packet of unflavored gelatin to 1/4 cup room temperature water and allow to bloom/rest for 1 minute. Pour and stir in 1/4 cup boiling water until the gelatin dissolves. Stir into the pastry cream and chill overnight.
Oil the bottom and sides of an 8-inch springform pan. Line the bottom with parchment paper. Line the sides with parchment paper about 8-inches high. You'll probably need three sheets of paper to do the sides. Oiling between the overlapping pieces will keep them stuck together. Oil the inside of the parchment paper; set aside.
Place about 1 tablespoon of espresso on a plate. I use a deep 10-inch paper plate. Place one cake layer on top and baste the top with additional coffee-chocolate liqueur mixture, including the sides. (I like to use a silicone basting brush for this step because it doesn't absorb any liquid.) Try to use about 3 tablespoons of the mixture for each cake layer. To do so, you'll need to try and avoid from basting over already wet areas. If you run out of the mixture, just make a little more. The cake can always withstand more moisture. It's a sponge! Just realize that the cake will also absorb the pastry cream when resting for several days.
In doubling a recipe, be sure to make the new calculations on a printed version of the recipe. It is extremely easy to make an error if you double the recipe calculations as you make the cake.
To make espresso using espresso powder, add 4 teaspoons espresso powder to 1/2 cup + 2 tablespoons boiling water and stir. (This is stronger than the suggested recipe on the Medaglia D'oro Instant Espresso Coffee bottle.)