Preheat your oven to 350°F (175°C) and line a cupcake pan with paper liners to prepare for baking.
In a large mixing bowl, sift together the flour, cocoa powder, baking soda, and salt to combine all dry ingredients evenly.
In a small bowl, dissolve the espresso powder in a tablespoon of hot water and set aside to cool slightly.
In another mixing bowl, whisk the eggs and sugar together until well combined and slightly frothy, about 1-2 minutes.
Add the melted butter, milk, vanilla extract, and the cooled espresso to the egg mixture, and whisk until smooth and combined.
Gradually fold the dry ingredients into the wet mixture, stirring gently until just combined and the batter looks silky and uniform.
Spoon the batter into the prepared cupcake liners, filling each about two-thirds full to allow room for rising.
Bake in the preheated oven for 18-20 minutes until the tops are slightly cracked and a toothpick inserted into the center comes out clean.
Remove the cupcakes from the oven and let them cool in the pan for 5 minutes, then transfer to a cooling rack for full cooling.
Once cooled, the cupcakes will be moist with a tender crumb, boasting a deep chocolate flavor enhanced by the subtle espresso note.
