I never had one when I lived in New York, but I found the recipe for this on the back of a Fox's U-Bet Chocolate Flavor Syrup bottle.

It has neither egg nor cream, but I think it gets its name from its frothy goodness. Here's the recipe:

Take a drinking glass, soda glass, fountain glass, whatever.

Add 1/2 inch of Fox's U-Bet Chocolate Flavor Syrup. OK, I know it's strange to measure volume in inches, but that's what the Fox's people did. And the closest their syrup gets to actual chocolate is that somebody Swiss once visited the Fox's U-Bet factory.

Add 1 or 2 inches of milk. I don't tolerate milk well, so you can use soy milk here with good results.

At this point, I like to stir to mix up the pseudosyrup with the quasimilk. The recipe says to stir later, but you can do both without too much regret.

Fill the rest of the glass with COLD seltzer -- in my experience it has to be really fresh so it has lots of gas. If already opened even an hour, it doesn't seem to work as well.

Stir (again).

Enjoy the frothy goodness.