Frosted Coffee (Serve in a ounce glass Coffee)

A soda-fountain formula written for someone standing at a counter with a syrup pump, a shaker, a carbonated-water draft arm and a bowl of cracked ice. Translated to a home kitchen it is a shaken iced coffee soda, and it comes together in under a minute.

• The syrup quantity is garbledThe syrup quantity may be garbled -- the plural in "Coffee syrup, ½ ounces" hints at a dropped numeral, and 1½ ounces would be in line with syrup pours found in comparable fountain formulas. Half an ounce in a 12-ounce drink would be lightly flavoured; if that tastes too thin, try 1½ oz (3 tablespoons) and adjust.
• Coffee syrupNot coffee-flavoured coffeehouse syrup but a thick sweetened coffee extract, still sold in New England under long-standing brand names. A workable substitute is equal parts strong cold-brew concentrate and sugar, warmed until dissolved.
• "Sweet cream"Period usage means fresh, unsoured cream as opposed to sour cream, not a sweetened one. Use light cream or half-and-half; heavy cream will make the drink cloying alongside the whipped topping.
• "Soda" means charged waterPlain carbonated water from the fountain, not a flavoured soft drink. Use well-chilled seltzer and pour it down the side of the glass so the carbonation survives.
• Ice and strainingThe text is compressed and its order ("fill with soda, strain") is hard to follow as written; fountain practice was generally to shake with cracked ice in a mixing tin and strain into the serving glass. Leaving the ice in the serving glass dilutes the drink and leaves no room for the whipped cream.
• What "frosted" meantAt the fountain the term generally indicated a drink enriched with cream or ice cream and shaken to a foam, as distinct from a plain soda, though usage varied between houses and manuals. It does not appear to mean a frozen or slushy texture here.
• YieldOne 12-ounce glass. The recipe scales directly.