AHi everyone!

I was just trying out a new recipe for dulce de Leche cupcakes. The buttercream calls for butter, sugar, heavy cream, vanilla, and you mix in the cooled dulce de Leche. The bc wouldn't harden and it's turned grainy with little bumps. The taste is great though, and when I tried to frost the cupcakes after a while the bc started to separate from the dulce de leche. This is the first time I've made bc from scratch and any help would be much appreciated! Here are some pictures, I didn't know if my descriptions were that great. [IMG]http://cakecentral.com/content/type/61/id/3031641/width/200/height/400[/IMG]

Without knowing your exact recipe and procedure, it is hard to say.  It sounds like the buttercream is breaking, or you've lost your emulsion.

 This happens when you try to put a liquid into a high fat.  You might be able to save it with some powdered sugar.  In the future, I would completely make the buttercream and then fold in the dulce in. Don't try to whip it in.
 

I agree, I would completely make the butter cream and the fold dulce de leche. usually I thin out the dulce de leche with heavy cream or milk.

AOh ok, thank you so much !! I'm definitely going to do that next time. This is the same for adding any liquid into a bc?