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Cocoa Icing
½ cup powdered cocoa 1¾ tablespoons butter 1½ cups white sugar Pinch of salt ⅓ cup milk 2 teaspoons vanilla To the milk and butter, add the cocoa, sugar and salt. Boil 8 minutes. Take off and beat until creamy. Add vanilla and pour over cake to depth of ⅓ inch.
This is a boiled fudge icing rather than a stirred buttercream, and it behaves like fudge: it sets hard once it cools, so everything after the beating stage has to happen quickly.
- Watch the temperature, not the clockEight minutes at a boil is an approximation from an era of unpredictable stoves. What matters is reaching soft-ball stage, 235-240F on a candy thermometer; a hotter finish gives a grainy, brittle icing and a cooler one never sets.
- Powdered cocoaThis means plain unsweetened cocoa powder rather than sweetened drinking chocolate. Sift it into the milk to avoid lumps that will not break down once the syrup boils.
- White sugarGranulated, not confectioners' sugar. Confectioners' sugar contains cornstarch and will not behave correctly in a boiled syrup.
- Beat off the heatTake the pan fully off the burner before beating. Beating develops fine sugar crystals, which is what turns the glossy syrup opaque and creamy; residual heat will keep the mixture too fluid and then it will seize suddenly.
- Work fast at the endAdd the vanilla and pour immediately. Once this icing starts to thicken it stiffens quickly and stops being pourable. If it stiffens too soon, a teaspoon of hot milk beaten in will loosen it briefly.
- Depth of one-third inchA generous coating by modern standards. The instruction is to pour it over the cake rather than spread it, so expect it to cover a top surface; judge the quantity against your own pan rather than assuming it will also cover the sides.
- Salt and butterThe pinch of salt is not optional in a mixture this sweet, and 1½ tablespoons of butter is roughly 20 g. Unsalted butter plus the pinch gives you control over the balance.
The Five Roses Cook Book was published by the Lake of the Woods Milling Company of Winnipeg and Montreal to promote its Five Roses flour, and like most milling-company books it was distributed cheaply and in enormous numbers across Canada in the 1910s and 1920s, ending up as the working kitchen manual in a great many households. Boiled cocoa icings of this type belong to the moment when cocoa powder became a cheap pantry staple: the Van Houten hydraulic press of the nineteenth century had made defatted cocoa affordable, and by the early twentieth century tins of it sat in ordinary kitchens where a block of chocolate once would have been a luxury. The method is simply fudge candy stopped at the right moment and poured, which is why the instructions read like confectionery rather than baking, and why the icing sets with a faint fudge-like snap instead of staying soft.