Heat oven to 350℉/177℃.
Line muffin tins with liners or spray with baking spray. Set aside.
In a medium bowl, whisk together flour, cocoa powder, espresso powder, baking powder, and salt. Set aside.
Beat butter and sugar in the bowl of an electric mixer until light and fluffy, about 2-3 minutes.
Add eggs, one at a time, beating well after each addition.
Stir in vanilla.
Add flour mixture alternately with milk, beginning and ending with flour mixture.
Portion batter into prepared muffin tins, filling each about ¾ full.
Bake for 15-20 minutes, until done.