Softened butter works best. You can use colder butter, but it will take much longer to get the nice smooth consistency you want and you may end up with flecks of unmixed butter in your frosting.
Sifted powdered sugar is better, but to be honest I never sift mine and it works just fine
For the dark chocolate, chips, bars, or anything else works since you’re going to melt it. Also, the darker the better! Even for those who don’t like super dark chocolate, I’d still use dark chocolate if you have it because there is so much sugar in the frosting itself, it will still be very sweet and the darker chocolate has a richer flavor.
Now normally I put vanilla in everything and usually about 3 or 4 times the recommended amount because I love vanilla extract. However, lately I haven’t been using vanilla in my buttercream and I’m finding it comes out just as good if not better, so the choice is yours.
Store your frosting in an airtight container in the fridge. If you’re planning to use it again, let it soften on the counter for several hours before using (you can stick it in the microwave for 10-15 seconds to help soften it if you’re short on time). It’s even better if you can whip it on high speed in your mixer for 30 seconds for a better consistency before you use it (this of course assumes that you have any left over and didn’t eat it all before needing to use it before, which is something I wouldn’t understand).
This recipe should be enough to frost and fill a 3-4 layer 6” round cake or any standard 8-9” round cake. I tend to use thick coats of frosting so I usually use more than expected.
Remember, this is a basic outline and you can experiment as you see fit to make more or less frosting or to change the flavor or consistency to your taste. The amounts I gave are loose averages for what I generally end up using.
Nutritional Information: You don’t want to know.