This section is from the book "Soyer's Standard Cookery", by Nicolas Soyer. Also available from Amazon: Soyer's Standard Cookery.
Three tablespoonfuls of butter, one cup of unsweetened powdered cocoa, two and a half cups of confectioners' sugar, few grains of salt, half cup of milk, one teaspoonful of vanilla.
Melt butter, add cocoa, sugar, salt and milk. Heat to boiling-point, and boil about eight minutes. Remove from fire and beat until creamy. Add vanilla and pour over cake.
 
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