Spoon vanilla ice cream or lightly sweetened whipped cream into two glasses.
Pour the rum and butterscotch schnapps over the cream.
Slowly pour in the cream soda, waiting for the fizz to setting down before adding more.
Sprinkle the top with nutmeg and serve.
Notes
Filling the glasses with the ice cream or whipped cream first will give you more of a yellow-colored, foamy glass of butterbeer that's a bit more traditional.
For a clear drink (as photographed in today's post) combine the rum, butterscotch schnapps and cream soda first, then add whipped cream on top.
For a non-alcoholic version, replace the rum and butterscotch schnapps with 1 tablespoon of butterscotch syrup or sauce.