Prepare the coffee crepes. Place all of the ingredients needed for the crepes into a blender. If your blender is smaller, split the recipe in half and prepare twice. Blend ingredients until smooth and clump free. If you don't have a blender, whisk all the liquid ingredients first. Then gradually sift in the flour, whisking until no clumps remain.
Preheat a 9-inch non-stick crepe pan or frying pan over medium heat. Add 1/4 cup crepe batter into the center and tilt pan to spread the batter evenly to the edges. Once edges of crepe turn golden, use a rubber spatula to flip the crepe over. Cook about 30 seconds on second side. Stack ready crepes onto a plate. Allow them to cool before assembling cake.
Preparing the Filling:
NOTE: These are updated instructions and prepared slightly differently from my video tutorial.
Place the softened butter into a mixer bowl and using a flat beater attachment, beat the butter for 5 to 6 minutes, until it's fluffy and creamy. Switch over to a whisk attachment and add in the mascarpone cheese and mix again until the cheese is smooth. (If using mascarpone cheese, do not soften it; use straight from the fridge!)
Next, add in the sweetened condensed milk, vanilla, salt and amaretto. Whisk again for about a minute, until well incorporated.
In a separate bowl, whisk the heavy cream until soft peaks form, then add to the butter and cheese mixture. Whisk on medium speed until light and fluffy. Be careful not to over-mix! Overmixed filling will separate.
Assembling the Cake:
Assemble the cake next. Line an 8-inch spring form pan with parchment paper. Drop a crepe into the pan first, followed by 1/4 cup filling. Spread the filling evenly to the edges, then sprinkle with cocoa powder. Continue with remaining crepes and filling. Leave the last crepe with no filling. Cover the crepe cake with plastic wrap and refrigerate overnight.
Once cake is set, invert the cake onto a cake platter. Remove the spring form pan, then dust the top with cocoa powder. Remove cake about 30 minutes prior to serving; otherwise, keep refrigerated.