It doesn't matter if I start out with chocolate, white, whatever recipe, my black buttercream almost always looks grainy without a uniform color. It's really a pain in the you know what.
And of course my friend doesn't want fondant accents, all buttercream please! With purple, blue, pink, etc... so the purple tastes bitter even though I used Americolor and started with a pink and the black look tastes bitter too.
Grrr! FBCT FTL! Off to Hobby Lobby to give in and buy premade black...
Most of my black starts of with store bought chocolate icing, add americolor black, and my buttercream and it comes out perfect each time, if you need a really shiny black icing add a little bit of piping gel.. the chocolate takes the bitterness out, but not too overpowering chocolate tasting either..
the one thing I don't like is after you eat a lot of black icing it turns your mouth black, steer clear for kids parties!!!
I use Toba Garrets chocolate butter cream recipe and add black. I've never had a problem with it being grainy.