Start off by mixing the soft butter and shortening together till nice and creamy on medium speed.
Turn the mixer down to the lowest setting and slowly incorporate the powdered sugar into the shortening mixture.
Once you have added all the sugar to the mix add in the hot water and the mint extract.
Turn the mixer up to medium-high speed and continue mixing for 10 minutes until light and fluffy.
Gently fold in the chocolate pieces.
Take big scoop of the frosting with your large cookie scoop and press it into the top of the cupcake pressing the button a few times to release the frosting. Repeat this with the other cupcakes.