This section is from the book "Meals Medicinal", by W. T. Fernie. Also available from Amazon: Meals Medicinal: With "Herbal Simples" Curative Foods From the Cook in Place of Drugs From the Chemist.
Practically Caudle, so called from the Latin "Calidus" hot, or the old French word "Chaudel," is a drink of warm ale made with groats, and given to the sick as a restorative support. It is more frequently composed of warm wine (or ale), mixed with bread, sugar, spices, and sometimes eggs; being administered specially to a woman in childbed (though with doubtful wisdom), and to her congratulatory visitors. "Hark ye, Master Hollytop! your wits are gone on wool-gathering: comfort yourself with a Caudle" (Sir Walter Scott's Abbot). For "tea Caudle, make a quart of strong green tea, and pour it out into a skillet (a long-handled metal pot), and set it over the fire; then beat up the yolks of four eggs, and mix with them a pint of white wine, a grated nutmeg, and sugar to taste; put all together; stir it over the fire till it is very hot, then drink it in china dishes."- Compleat Housewife, 1736.
When Harley (in the Man of Feeling, 1771) "came downstairs to set out for London, he found his aunt in the parlour with a tear on her cheek, and her caudle cup in her hand; she knew enough of physic to prescribe against going abroad of a morning with an empty stomach: and she gave her blessing with the draught".
For old-fashioned brown Caudle: stir two tablespoonfuls of oatmeal into a pint of water, and add the thin rind of a lemon, a blade of mace, and a tablespoonful of brown sugar. Let all boil together: then strain the liquid, and add a pint of mild ale. Warm it for use. A little grated ginger is often put into this Caudle. The old-fashioned Caudle-pot was of glazed Delft-ware, holding about a quart, and having a small curved spout which went into the mouth of the drinker. Such a pot (now much sought after by collectors) is to be seen among the treasures at Lilford Hall, Northants.