1 1/2cupsunsalted butter(3/4 lb), cut into 1-inch cubes
2227 g containerswhipped cream cheese
1Tablespoonpure vanilla extract
Roughly chop the chocolate into chunks. Place in a double boiler or in a bowl set over a pot of simmering water. Melt slowly, stirring occasionally.
Remove the bowl from the pot and cool the chocolate to room temperature.
In the bowl of a stand mixer fitted with the whisk attachment, beat together the butter and cream cheese until light and fluffy, at least 5 minutes. Stop the mixer and scrape down the sides of the bowl once or twice.
Add the cooled chocolate, vanilla and salt; beat until thoroughly combined.
Turn off the mixer and add the powdered sugar, one cup at a time. Beat on low speed until combined. Increase the speed to High and beat for one minute.
Frosting is best used within 30 minutes or so of making, when it is still easily spreadable. As the chocolate hardens, the frosting will stiffen somewhat.