Preheat oven to 175°Celsius.
Prepare cupcake liners.
In a small cup, dissolve instant coffee powder with hot water. Mix and set aside to cool.
In a separate bowl, cream the butter and sugar until light and fluffy.
Add the eggs, one at a time. Beat well after each addition.
Sift flour, baking powder and salt. Fold into the creamed mixture alternately with milk. Start and end with flour.
Finally, fold in the dissolved coffee and mix until the coffee is well distributed and the batter is evenly colored.
Scoop the batter into prepared cupcake casings and bake for approximately 20 minutes. The top of the cupcakes should spring back when lightly pressed.
Remove cupcakes from oven and let them cool down completely before frosting.
To make the coffee buttercream, dissolve the coffee in hot water. Set aside to cool.
In a medium-sized bowl, beat butter and shortening until soft and creamy.
Add in the sifted powdered sugar and beat until smooth.
Pour the coffee solution and continue to beat the buttercream until the coffee is evenly distributed in the buttercream. Add some milk or cream if the consistency is too stiff.
Fill the coffee buttercream into a piping bag fitted with a large star tip and pipe simple swirls on each cupcake. Top with a milk chocolate button.