I would love to know how you did this effect!!!  I love how you did this!  Could you please let me know?  Did you first ice the cake in white buttercream and then smear the black on?

I frosted it in white Swiss meringue buttercream, and then I diluted a drop of black americolor gel color with just a bit of vodka. Then I dipped a paintbrush into the black color and flicked it all over the cake. Then I used my offset spatula to smear the splattered dots around. Cover your kitchen with newspaper and wear an apron - this makes a MESS!

Thanks for getting back with me!!  I appreciate it!  I'll be using an American Buttercream.  Should I let it crust before I start in with the black color?

no, it should be fresh so it can smear well.

Thank you!