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Lemon Icing
1 egg yolk. 1 cup sugar. 1 lemon (grated rind and juice) Mix all ingredients thoroughly and put in double boiler, Cook 15 to 20 minutes.
Let cool and spread between cakes.
As printed, this entry has lost most of its ingredient list — only the lemon survives, followed by instructions that refer to "all ingredients." What remains is still readable as a method, but the proportions are genuinely missing and cannot be recovered from the page.
- The ingredient list is incompleteOnly "1 lemon (grated rind and juice)" is given, yet the method says to mix all ingredients. Comparable cooked lemon fillings of the same era combine the lemon with sugar, egg or egg yolk, a little butter, and sometimes water thickened with cornstarch or flour — but this book does not state the quantities here, and guessing them is not the same as reading them.
- It is a filling, not a spreading icingDespite the heading, the final line says to spread it between cakes. Without the rest of the ingredient list there is no way to tell from the page how stiff the cooked mixture was meant to set.
- Double boiler means gentle, indirect heatWater in the lower pan should stay at a bare simmer and must not touch the upper pan. Egg-thickened lemon mixtures curdle over direct heat or in a rolling boil; steam is the point.
- About that 15 to 20 minutesThat range assumes a thin, flour- or starch-set filling stirred over water. If the mixture is egg-based, it is done when it coats a spoon and holds a line drawn through it — usually well before 20 minutes. Cooking on past that stage gives a grainy, slightly sulphurous filling.
- Zest before juicingGrate only the coloured outer layer; the white pith underneath is bitter and will not soften in cooking. Adding the zest at the start extracts more of its oil than stirring it in at the end.
- Cool completely before spreadingWarm filling slides and soaks into the crumb. Press a piece of plastic or buttered paper directly on the surface while it cools to keep a skin from forming.
- Yield and keepingKeeping -- If the missing ingredients included egg and butter, as comparable fillings of the era did, keep the finished cake refrigerated and eat it within two or three days. The yield cannot be worked out from the page, since only the lemon is given.
Cooked lemon fillings sit in nearly every North American community and promotional cookbook of the early twentieth century, where frostings and fillings were often treated as one family of finishing mixtures rather than distinct techniques. The Five Roses Cook Book was published by Lake of the Woods Milling Company to sell Five Roses flour, and its recipes were largely gathered from Canadian housewives who used the brand, which is why entries are often terse and occasionally, as here, incomplete — though a missing ingredient list may as easily be a printing or transcription loss as anything else. The double boiler itself was a fixture of the period kitchen, valued precisely because wood and coal ranges gave uneven, hard-to-moderate heat, and any egg-thickened mixture stood a better chance over water than over a firebox.