Preheat your oven to 350°F (175°C) and line a cupcake pan with paper liners.
In a large mixing bowl, whisk together the flour, sugar, baking powder, baking soda, salt, and cocoa powder until well combined.
In another bowl, mix the cooled coffee, vegetable oil, eggs, and vanilla extract until smooth.
Gradually add the wet ingredients to the dry ingredients, stirring until just combined. Do not overmix.
Divide the batter evenly among the cupcake liners, filling each about two-thirds full.
Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Remove from the oven and let the cupcakes cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.
While the cupcakes are cooling, prepare the buttercream frosting. In a large bowl, beat the softened butter with an electric mixer until creamy.
Gradually add the powdered sugar, mixing on low speed until combined. Add the heavy cream, vanilla extract, and brewed coffee, then beat on high speed for 2-3 minutes until fluffy.
Once the cupcakes are completely cool, frost them with the buttercream using a piping bag or a knife.
Serve immediately or store in an airtight container at room temperature for up to 3 days.