In a large mixing bowl using an electric hand mixer, beat the cream cheese and butter together until smooth. Scrape down the bowl and beat again to make sure there are no lumps.
8 oz (226 grams) Full fat cream cheese, 4 tablespoons (56 grams) Unsalted butter
Sift in the powdered sugar and cocoa powders, add the vanilla extract and beat starting on low speed and increasing the speed to high. Beat until fully combined and smooth.
Add the heavy cream and beat on medium/high speed until smooth and fluffy, about 1 minute. Refrigerate until ready to use.
4 tablespoons (60 grams) Heavy whipping cream
Notes
If you can’t find black cocoa powder you can substitute all 6 tablespoons of cocoa for a dark cocoa such as Hershey's Special Dark. It won’t be as dark as if you use black but it will still be yummy.