1 pint heavy cream
2 tbsp sugar
2 tsp to 1 tbsp vanilla extract
And that's it!
Get out your stand mixer with the whisk attachment (you can pop the mixing bowl in the freezer for 20min prior to whipping to help the cream stiffen up, but I don't usually find this necessary.) Add heavy cream, sugar and vanilla, and whip on high until nice and fluffy. Using the full pint will make enough for many many butterbeers, so if you're not having guests you may want to half it.
Measure one standard shot glass of Buttershots (or as much as you want!) and add to a tall glass. Fill glass with cream soda, and top with a generous dollop of fresh whipped cream. The end!
I know I mentioned before that I'm not a drinker. I don't like anything that you can taste the slightest hint of booze in. And even with drinks I do like, it's usually one and I'm all done. Butterbeer is the exception. I could drink these all night, although usually I take a look at the amount of cream and sugar I'm consuming and stop after two. But it's not easy.
Now, because I wouldn't be a true geek if I didn't address the matter of authenticity: Butterbeer is served both hot and cold, and I would not want to taste this recipe hot! It's also probably sweeter than Rowling intended. But I think it is a pretty darn good (and definitely delicious) approximation. The butterbeer in the books always seemed ambiguously alcoholic to me, which is about right for the strength I make this drink. With your witch's hat on and a glass of butterbeer in hand you'll feel like taking a trip to Hogsmeade.
If you're serving to kids, you can leave out the Buttershots and use a 1/2 tsp to a teaspoon of artificial butter flavoring. I feel kind of weird about drinking that, but it does give it a more butterscotchy flavor without the booze.
As I type this I'm enjoying my first butterbeer of the year, sporting a whipped cream mustache and a smile. You can always stir the whipped cream in with a spoon to make it easier to drink and give it a thicker texture and more even creaminess. Either way, it's delicious!