Preheat the oven to 325 degrees with the rack in the center.
Grease one and a half madeleine pans with shortening.
In a microwave safe bowl, mix butter, sugar, chocolate, espresso together. Heat for 1-2 minutes on low power. Stir the mixture until smooth.
Allow to cool for 3-4 minutes. Whisk in the egg until thoroughly mixed.
Stir in the flour and cocoa. Baking powder
Fill the shell molds with batter until it’s almost full. Do not overfill the cavities.
Bake for 12 minutes.
Allow to rest for 5 minutes in the pan.
Cool on the dish towel for 25 minutes.
Serve.