Use either veal or mutton kidneys; cut them up small, saute in butter over a brisk fire, drain and put them back into the pan with half-glaze sauce (No. 413) and white wine; take out the kidneys, reduce the sauce, butter it and replace the kidneys to warm up again, then fill the inside of an omelet with the preparation, and finish it as the Argentine (No. 2878), pouring the sauce around just when ready to serve.
A stuffed omelet from Ranhofer's The Epicurean (1894), written in the shorthand of a professional kitchen that assumed a stocked sauce station. The two cross-references do most of the work, so they need filling in before you start.
Charles Ranhofer ran the kitchen at Delmonico's in New York, and The Epicurean is essentially that restaurant's working repertoire set down in print, complete with the internal numbering that let a cook chase a sauce back to its source. The omelet chapter alone runs to dozens of variations, each defined by its garnish, which is how a nineteenth-century grand kitchen turned a handful of eggs into a long menu section. Kidney belongs there because organ meats were neither cheap nor apologetic on such a menu: rognons sautés with madeira or white wine and a brown sauce were standard French bourgeois and restaurant cooking, and folding them into an omelet gave the kitchen a dish that could go out at breakfast, at supper after the theatre, or as an entrée in the middle of a long meal. The pattern of searing the kidneys, removing them, reducing the sauce, then returning them to warm through is the classic French handling of the cut, and something close to it is still widely followed in professional kitchens.