Spoon a scoop or two of vanilla ice cream into a tall glass.
Slowly pour root beer into the glass, allowing the foam to rise and then recede before adding more root beer.
Serve with straws and spoons.
If you want to make this into an "adult" beverage, use one of the alcoholic root beers (our favorite is "Not Your Father's Root Beer" which we buy locally at BevMo). This is delicious. (But a little dangerous because it tastes so good!)