Heat oven to 350 degrees and line a 12-cup cupcake/muffin tin with liners.
Sift the flour, baking powder, baking soda, cocoa powder, sugar and salt. Mix well.
Make a well in the center of the dry ingredients and add the melted butter, buttermilk, eggs, vanilla and coffee. Blend until there are only a few small lumps left.
Scoop into lined cupcake tins and bake for 20 minutes or until the centers spring back when lightly pressed.
Cool for three minutes in the pan before removing the cupcakes to a wire rack to cool completely.
2 tsp very hot water
1/4 tsp salt
1 (7 oz) jar marshmallow cream
1/2 cup shortening
1/3 cup powdered sugar
1/2 tsp vanilla
Dissolve the salt in the hot water and allow to cool.
Whip the marshmallow cream, shortening, powdered sugar, and vanilla until it begins to get fluffy. Add the water and whip well.
To fill the cupcakes, use a wide star tip (size 21) attached to a coupler on a piping bag. Just lightly push the tip into the top of the cupcakes and press approximately a tablespoon of filling inside. If you do not have a piping bag, you can just cut out a little bit of the cake from the top, make a hole, fill the hole with filling then top with cake you cut out.
Prepare the frosting
6 TBSP butter, softened
1/2 cup dutch processed cocoa powder
2 1/4 cup powdered sugar
1 tsp vanilla
4-6 TBSP milk or half & half
Cream the butter and cocoa powder until smooth.
Add the vanilla, powdered sugar and milk. Mix until smooth. If the frosting is too loose add more powdered sugar by the 1/4 cup until it reaches the desired consistency.
Frost as desired.