https://livetosweet.com/2024/06/15/buttermilk-frosting/#recipe

You can make that above recipe by adding cocoa to the frosting and blending well. May need a bit more moisture so use more buttermilk, of course!!

AND then there's my favorite buttermilk icing!  The difference between icing and frosting has been so bastardized over the past 10 years most people don't really have a clue that there's a difference.  It's actually hard to find "icing" recipes online anymore.  Icing is much thinner, doesn't require more than about 4 ingredients and doesn't require any cooking at all.

BUTTERMILK ICING

• 1 cup powdered sugar, sifted 
• 2 tablespoons cultured buttermilk 
• 1 tablespoon melted unsalted butter 
• ½ teaspoon vanilla extract or paste 

Stir together, make it quite thin in consistency, and pour it wherever you want it to be!  I like to use almond extract in mind depending on what I'm using it for.  For a Bundt cake, for instance, I keep it quite runny and just sort of drizzle it over the cake and let it slide down the inside and outside.  Wow I'm hungry for cake now (chocolate of course!) with buttermilk icing!