Orange Filling
To the juice and grated rind of one orange add enough powdered sugar to make a stiff paste. Spread between the layers of a cake, icing the top layer.
An uncooked filling of the simplest kind: acid, aromatics and sugar worked to a spreadable paste. The whole thing hinges on how much sugar you add, which the original leaves to your judgment.
- How much sugarOne medium orange gives roughly 1/4 to 1/3 cup of juice, which will take several cups of powdered sugar before it stops running. Add it in stages, beating smooth each time, and stop when a spoonful holds its shape.
- Powdered sugar then and nowPeriod powdered sugar was ground cane sugar, sometimes without added starch. Modern confectioners' sugar contains about 3 percent cornstarch, which thickens the paste slightly faster and gives it a marginally chalky finish; it is otherwise a direct substitute.
- Zest before juicingGrate the rind while the orange is whole and firm. Take only the coloured layer, since the white pith underneath is bitter and will not dissolve into the sugar.
- Strain the juicePulp and membrane make a lumpy filling. Push the juice through a fine sieve first, and let the zest carry the flavour.
- Consistency for layeringAim for a paste stiffer than icing, close to soft fondant. Anything looser will be squeezed out by the weight of the upper layer and soak the crumb.
- Icing the topThe recipe says only to ice the top layer and does not say with what. If you mean to use the same mixture, set some of it aside before you fill the cake.
- Yield and keepingOne orange's worth makes enough to fill a small layer cake, depending on how much sugar you work in. It contains raw juice and no fat, so it will weep and form a crust if made far ahead; mix it the day you assemble the cake.
Uncooked sugar pastes like this one were an alternative to a boiled or custard filling: no double boiler, no eggs, no risk of curdling, and nothing to cool before the cake could be put together. They relied on cheap refined powdered sugar and on citrus that travelled, both of which were increasingly available to American kitchens by the late nineteenth century as Florida and California groves and refrigerated rail freight expanded. The recipe says nothing about what kind of cake to spread it on, leaving the cook to pair it with whatever plain layer cake she already knew.