Combine 1 1/8 cup sugar, flour, cocoa powder, baking powder, salt, and baking soda in a mixing bowl. Mix well using a balloon whisk. Set aside.
In another bowl, combine eggs, milk, vegetable oil, and vanilla extract then mix using a stand or hand mixer.
Gradually add the flour mixture while mixing. Continue mixing for about a minute.
Pour-in hot water then mix until everything is well incorporated. Set aside.
Preheat oven to 350 degrees Fahrenheit.
Line the cupcake pan with muffin cups then pour-in the batter.
Bake for 18 to 22 minutes.
Remove from the oven and place in a wire rack to cool.
Sprinkle graham crackers on the cupcakes.
Make the frosting. Pour water in saucepan then turn-on heat. Allow the water to reach the point where it is near boiling.Place a glass or metal bowl over the saucepan then combine sugar, cream of tartar, and egg whites. Whisk continuously for 4 to 5 minutes. Turn off heat.Remove the bowl from the saucepan then whisk the mixture using an electric or stand mixer until stiff peaks form (about 6 minutes in high speed).Add vanilla extract then mix for 30 seconds.
Place the frosting in a piping bag then pipe over the cupcake.
Transfer to a cupcake rack or serving plate then serve. Share and enjoy!