Rich Chocolate Buttercream

Ingredients

Melt the butter in a large saucepan and whisk in the cocoa powder then remove from the heat and let cool.
Add the cooled chocolate mixer to your stand mixer and whip on medium speed adding the powdered sugar and sour cream, alternating them 1/3 at a time.
Add the vanilla in last.
If the frosting is too thick, add a bit more milk 1 tablespoon at a time. (Be careful with this, it's very easy to over-do it and make the frosting runny)

Use 2 (14oz) cans of sweetened condensed milk instead of powdered sugar. Add it in the same step powdered sugar would be added.