Whites of eggs are nearly always the last thing to be put into any mixture, because if they are moved about more than is necessary to get them in, much of the air in them will be lost.
The ingredients of cake are usually mixed in the following order: butter and sugar beaten together to a creamy consistency; beaten yolks of eggs; milk or water and flavouring; flour and baking powder; whites of eggs.
The order for mixing a sponge cake is the same except that some of the ingredients mentioned in this list will be omitted.
The reason that flour is put in last, or next to the last, is that it contains the baking powder or the soda and cream of tartar. When these substances are wet they give off gas which is to make the cake light, therefore they should not be wet until just before the cake is ready for the oven.
Fruit is put into a cake last of all. It is floured before it is put in to keep the pieces from sticking together, and to keep the moisture they contain from injuring the cake.
Because the lightness of cake depends upon bubbles of air or gas which in the course of time collapse, cake batter should be baked as soon as mixed. That this may be possible, the fire should be put into suitable condition and the utensils and materials gathered and prepared before the mixing begins.
Pastry.—Pastry mixtures differ from bread or cake mixtures in that they are flaky instead of spongy. Things flake when they are composed of layers; the point then is to make pastry by a process which will produce layers. When a smooth dough has been made of flour, salt and cold water, it is rolled lightly to a thin sheet, tiny pieces of butter are scattered over it and a very little flour sprinkled on it. The sheet is then doubled, rolled to the former thickness, butter and flour are applied to it as before and it is again doubled. This is repeated several times. When it is finally ready for the oven it is in layers of dough and butter. When the heat of the oven melts the butter and expands the air between the layers, they separate a little, that is, they flake.
By means of this theory of pastry one can better understand the directions given in pastry receipts. For example, the ingredients must be kept cold that the butter and dough may not combine during the rolling. The pastry must be handled lightly and never pressed or pounded because this would press out the air and crush the layers into each other.
The filling of pies sometimes presents difficulties. A very juicy filling soaks the under crust. One remedy used for this is to bake the bottom crust before filling the pie; another is to brush it over with white of egg. The very best way to prevent the under crust of a pie from being soggy and indigestible is not to have one. Put the fruits into a fairly deep baking-dish and cover it with a flaky top crust. This is an English method which we should do well to follow. The result is more fruit and less crust, and none of that under crust which whatever pains you take will more or less relapse into dough.