Preheat your oven to 350°F (175°C) and line muffin tins with cupcake liners.

In a large bowl, whisk together the all-purpose flour, cocoa powder, baking powder, and granulated sugar.

In another bowl, mix the eggs, milk, and vegetable oil until smooth.

Fold the wet ingredients into the dry ingredients gently until just combined.

Fill each muffin tin two-thirds full with batter and bake for 18–20 minutes until a toothpick inserted comes out clean.

While the cupcakes cool, whip the mascarpone cheese with the espresso until fluffy.

Cut the tops off the cooled cupcakes, scoop out a small amount of the center, and fill with the mascarpone mixture, then replace the tops.

Dust the tops with cocoa powder and serve at room temperature.