Peel and cut up four middling-sized onions into very small dice, put
them into a stewpan with two ounces of butter, stir them over a moderate
fire until rather brown; then add two tablespoonfuls of common vinegar,
let it boil; then add a pint of brown sauce (No. 1), with half a pint of
consommé (No. 134), let it simmer at the corner of the stove ten
minutes; skim it well, then stir it over a sharp fire, reducing it until
rather thick; finish it with two tablespoonfuls of French mustard, a
little sugar, and salt, if required.