This section is from the book "Cooking For Profit", by Jessup Whitehead. Also available from Amazon: Cooking for Profit.
Aspic is the French cooks' name for it. It is the jelly formed by boiling meat down till the liquor will set when cold, the jelly, for example of head cheese, or of boiled chickens when the liquor has nearly all boiled away,and if it is the intention to make jelly of such liquor an extra calfs foot or pig's foot or two will be thrown in at the beginning of the boiling and make the liquor stronger. This being the jelly in the rough state - seasoned as soup would be to make it taste good and relish -- in order to change its appearance from dull gray into an article of sparkling transparency it is necessary to clarify it by boiling white of eggs and lemon juice in it and straining it through a flannel jelly bag.
The making of savory jelly is not an abstruse and foreign affair, but anyone who takes pleasure in such things finding at hand some meat liquor that has set in jelly firm enough to cut with a knife can clarify it and use it to set off a luncheon or supper table in a way that is by no means common.
But when there is no meat jelly already formed make some by dissolving an ounce of sheet gelatine in a quart of good soup ' stock, season it nicely, let it get quite cold to remove the grease, then melt and clarify it as for sweet jelly at No. 465.
Make different tints by adding burnt sugar dissolved in boiling water for amber and brown, and cochineal or beet juice for pink and red.
Extra fine jelly, more brilliant than is ever seen in the restaurant windows, is made by putting it through the clarifying process twice, allowing a little in the measure for the inevitable loss of quantity in the repeated boiling and filtering; and a correspondingly enhanced flavor is obtained by adding a proportion of sherry.
 
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