Preheat your oven to 350 degrees F. Line a muffin pan with paper liners and set aside.
In another bowl, whisk together together sugar and eggs until creamy.
Add oil and coffee to your egg mixture. Whisk until well-combined.
Add boiling water into your mix and whisk some more.
Cool completely on wire rack before decorating.
To make mocha frosting, beat together butter, powdered sugar, milk, coffee and cocoa powder using an electric mixer.. Start on slow speed and gradually increase to high.
The buttercream is ready once all ingredients are thoroughly combined, smooth and form semi-stiff peaks.
Scoop buttercream into a large piping bag with Wilton tip #1M attached. Frost each cupcake by piping in a circular motion, starting at the edge and ending in the middle.
Yields 18 to 22 cupcakes. The coffee in this recipe is more subtle while the chocolate is more prominent. Use strongly brewed coffee to bring out more of a coffee flavor.