¾cupconfectioner's sugaralso known as icing sugar or powdered sugar
Melt The Chocolate
Pour enough water into the bottom of the double boiler (or the pot you are using) to cover the bottom of the pan about 1/2" deep.
Bring the water to a boil, then turn the temperature down to medium-low.
Place the top half of the double boiler (or the large bowl) over the boiling water.
Add the chocolate chips (or chopped up chocolate).
Heat until you see the chocolate starting to melt. Then stir until all of it has melted.
Remove from the heat and let cool completely before using, about 30 minutes.
Make The Frosting
Combine the cocoa powder and hot water in a mixing bowl. Stir until smooth and set aside.
Add the butter to the electric mixer and beat until fluffy at a medium-high speed.
Mix in the confectioner's sugar and the salt.
Beat some more until the butter has turned a pale yellow color.
Turn the mixer speed down to low.
Mix in the cooled, melted chocolate until it is combined.
Beat in the cocoa mixture.
The frosting can be stored in an air-tight container in the refrigerator for up to 5 days, or up to a month in the freezer. To use, take it out of the refrigerator or freezer a few hours ahead of time to let it warm up to room temperature. Then beat on low for a few seconds until it is smooth again.