Mocha Icing
1/4 teaspoon vanilla About two tablespoons cold coffee Cream butter, add sugar and cocoa gradually. Add vanilla then coffee gradually until the mixture is smooth, creamy and thick enough to spread.
This is a plain uncooked butter icing, and as printed here the ingredient list has been cut short — only the vanilla and coffee survive, though the method calls for butter, sugar and cocoa as well. Work by texture rather than by measurement.
- The missing quantitiesThe original list gives no amounts for butter, sugar or cocoa. A workable ratio for this style of icing is roughly 1/4 cup softened butter to 2 cups confectioners' sugar and 2 to 3 tablespoons cocoa, but that is a reconstruction, not what the book printed.
- Sugar means confectioners'An uncooked spreading icing of this period assumes powdered or "XXXX" sugar. Granulated sugar will not dissolve in cold coffee and butter, and the icing will stay gritty.
- Cocoa, not chocolateCocoa here is unsweetened powder, the Dutch-process or natural tin of the era. It should be sifted with the sugar; dropped in whole it leaves dry specks that never break up.
- Cold coffee is the controlThe coffee is the only liquid and does double duty as flavour and consistency adjuster. Add it a teaspoon at a time; the book's 'about two tablespoons' is a guide rather than a fixed amount, and strong brewed coffee, cooled, gives more flavour than the dregs of the breakfast pot.
- Temperature of the butterButter should be soft enough to cream but not oily -- cool room temperature. Butter that is too warm takes up the sugar quickly and then slumps off the cake as it stands.
- When it is thick enoughIt should hold a soft peak and fall reluctantly from the spatula. If it goes too slack, more sifted sugar rather than more butter is the fix.
- YieldThe reconstructed quantities above make roughly a cup and a half of icing: enough for the top and sides of a single 8- or 9-inch layer, or about a dozen cupcakes. A two-layer cake would need more.
"Mocha" in American cookbooks of this era rarely meant a specific bean from the Yemeni port of al-Mukha, whose name the word carries; by the early 1900s it was widely used as shorthand for coffee flavouring, and in confectionery often for coffee and chocolate together. Uncooked butter icings like this one belonged to the newer end of the cake repertoire -- older books lean more on boiled sugar icings and beaten egg-white frostings, which set hard and keep, while a creamed butter icing depends on refined powdered sugar and is best eaten within a day or two. Using cold leftover coffee in this way is a frugality that turns up in other period cakes and puddings, though nothing on this page identifies the kind of book it came from.