Preheat an oven to 350°F/175°C. Line 12 muffin cups with liner papers.
In a large bowl, whisk together flour, granulated sugar, brown sugar, cocoa powder, baking soda, baking powder and salt. Set aside.
In a medium bowl, whisk together eggs, oil, buttermilk and vanilla extract until combined. Slowly add the wet mixture into the dry mixture and mix just until combined.
In a different cup, add the instant espresso powder into the boiling water and mix until dissolved, then add to the mixing bowl and stir to combine. Keep whisking until the batter is fully combined and smooth.
Evenly distribute your batter between the cupcake liners, filling no more than 3/4 full. Bake for 18-20 minutes until a toothpick inserted into the center comes out clean. Let the cupcakes cool in the pan for about 10 minutes then transfer them to a cooling rack to cool completely.