I did a cake in choc buttercream tonight. I do these maybe once a year. I make my usual buttercream recipe (1 1/3C Crisco to 2# Pwd sug-so it should crust, right??). I added the cocoa that had been dissolved in warm water & cooled to room temp. I do not usually dissolve the cocoa, but read that it would give the icing a nice, shiny finish. I couldn't tell a differnce!
My chronic problem with choc butter cream is that is seems that the longer it is worked with-stirred, piped, whatever-it gets softer. I even started with it stiffer from the mixer and it still got soft. I struggle to smooth it on the cake, it kind of wrinkles and slides a bit. It just acts weird.
What should I do differently?? Thank you!

I add melted chocolate instead of cocoa powder--works great.

I just use the recipe on the side of the Hershey cocoa can when I need a chocolate icing. Crusts well and easy to work with.

My chocolate buttercream isn't shiny but I add dry cocoa powder before I start adding the PS so that the cocoa powder is mixed in well. I also find it takes a lot more liquid to get the right consistency. After

does it matter if it is melted semi sweet chips or unsweetened squares?

I've used both, don't think it matters too much, it may take a bit longer to mix in the melted chips, because they are thicker.