I see there are already quite a few butterbeer recipes here, but.....

Just found this, if anyone wants it.

Lenona.

From the HP newsgroup:

Harry Potter's Butterbeer Recipe

According to reports, the #1 food item at the new Universal "Wizarding
World of Harry Potter" is "Butterbeer". The crowds are loving this
cold drink that's a staple in the Harry Potter books!

Here's the "unofficial" recipe that's already floating around on the
web - it seems to be a close version of the real thing, according to
taste tests anyway. So if it will be awhile before you can see the
attraction, your kids will love making this magical brew right at
home!

BUTTERBEER

Start to finish: 1 hour (10 minutes active)
Servings: 4

1 cup light or dark brown sugar
2 tablespoons water
6 tablespoon butter
1/2 teaspoon salt
1/2 teaspoon cider vinegar
3/4 cup heavy cream, divided
1/2 teaspoon rum extract
Four 12-ounce bottles cream soda

In a small saucepan over medium heat, combine the brown sugar and
water. Bring to a gentle boil and cook, stirring often, until the
mixture reads 240 F on a candy thermometer.

Stir in the butter, salt, vinegar and 1/4 cup heavy cream. Set aside
to cool to room temperature.

Once the mixture has cooled, stir in the rum extract.

In a medium bowl, combine 2 tablespoons of the brown sugar mixture and
the remaining 1/2 cup of heavy cream.

Use an electric mixer to beat until just thickened, but not completely
whipped, about 2 to 3 minutes.

To serve, divide the brown sugar mixture between 4 tall glasses (about
1/4 cup for each glass). Add 1/4 cup of cream soda to each glass, then
stir to combine. Fill each glass nearly to the top with additional
cream soda, then spoon the whipped topping over each.