Put a pound of powdered white sugar into a deep pan, and cut up in it a pound of fresh butter. Stir the butter and sugar together till perfectly light. Then add a powdered nutmeg, a table-spoonful of powdered mace and cinnamon mixed together, and a large wine-glass of excellent brandy. If the brandy is of bad quality it will give the cake a disagreeable taste. If very good, it will highly improve the flavour, and also add to the lightness of the cake. Sift into a pan a pound of flour. In another pan beat six eggs till very thick and smooth. Stir them gradually into the butter and sugar alternately with the flour, and a pint of rich milk or cream, a little- of each at a time. Have ready a level tea-spoonful (not heaped) of pearlash, or sal-eratus, (or a full tea-spoonful of bi-carbonate of soda,) dissolved in as much warm water as will cover it. Add this at the last, and then give the whole a very hard stirring. Butter a large square pan. Put in the mixture. Set it immediately into the oven, and bake it thoroughly. It requires very long baking. A thick square Boston cake will scarcely be done in less than three hours. At the end of the first hour, increase the heat of the oven, and also at the second. When cool, sift powdered sugar over it, and cut it into squares.
If properly made, and well-baked, (following exactly the above directions,) this cake will be found excellent, and will seem fresh longer than any other; the milk keeping it soft.
Milk turned sour is very good for Boston cake; as by stirring the dissolved pearlash or soda into the milk, the acidity will be entirely removed, and the alkali rendered more effective in increasing the lightness of the cake. Still great care will be necessary in baking it.
The best confectioners make this cake every day without any failure.