Preheat oven to 350°F. Line a muffin pan with 12 liners and set aside.
In a medium bowl, whisk together flour, cocoa powder, baking soda, espresso powder and salt. Set aside.
In a large bowl, mash avocado to make it as smooth as possible. You can toss it in a food processor to get it really smooth if you’re low on time (or energy).
Add flour mixture and stir to combine.
Now add sugar, water and vanilla, stir to combine until smooth.
Using a ¼ measuring cup, pour batter into cupcake liners until almost full. Bake for 17-20 minutes. A toothpick inserted into the center should come out clean, and the tops should be cracked a bit and spring back when touched. Set on wire rack to cool completely.
Place egg whites, sugar and cream of tartar in a double broiler over a simmering pot of water.
Whisk constantly until the sugar has dissolved and the mixture is foamy.
Pour egg white mixture into a large mixing bowl and whip on high speed with a whisk attachment until it forms stiff peaks.
Pipe frosting onto cooled cupcakes and garnish with crushed graham cracker and chocolate sauce. Enjoy!
Don't want to use avocado? Just substitute 1 cup unsalted butter, room temperature.