Set the oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners or grease lightly.
In a large bowl, whisk flour, sugar, cocoa powder, baking soda, baking powder, and salt.
In a separate bowl, mix cooled coffee, buttermilk, oil, egg, and vanilla. Pour wet into dry ingredients and stir until smooth. Don’t overmix. Fill each liner 2/3 full.
Bake for 18–20 minutes or until a toothpick comes out clean. Cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.
In a small saucepan, heat cream and instant coffee over low heat until dissolved. Cool for 5–10 minutes. Whip with powdered sugar and vanilla until soft peaks form. Chill until ready to use.
Use a knife or cupcake corer to remove the center of each cooled cupcake. Spoon or pipe the coffee cream into each hole. Replace the tops if desired.
Ganache: Heat cream until hot. Pour over chocolate chips, wait 2–3 minutes, then stir until glossy. Drizzle over cupcakes.
Buttercream: Beat butter until fluffy. Gradually mix in powdered sugar, brewed coffee, vanilla, and salt until smooth. Pipe on top.
Garnish with cocoa powder, chocolate curls, or coffee beans. Serve at room temperature.