Delicious, though sort of fudgy. I substituted 1/4 tsp of peppermint extract for the 1/16 tsp peppermint oil and ran out of cocoa powder and used peppermint hot chocolate mix instead. Cooked forever and stuck to the pan (I shouldn't have skipped the parchment paper) but so worth it.
Delicious! Lighter than expected but good - the flavor reminded me of peanut butter fudge. Very easy to make - just like normal buttercream but with peanut butter. Great on chocolate cupcakes!