Hollandaise Sauce

This is a compound-sauce entry rather than a standalone recipe: it takes a base sauce made elsewhere in the book and turns it into a sharp, pickly sauce for oysters. Everything hinges on what the period meant by "brown Hollandaise."

• "Brown Hollandaise" is not modern hollandaise"Brown Hollandaise" is probably not modern hollandaise -- in American household books of this era "Hollandaise" or "Dutch sauce" was used loosely, often for a stock-based sauce sharpened with vinegar or lemon and enriched with butter and egg yolk; a "brown" version would most likely have been built on a browned roux and brown stock, though this entry does not say. If you build a true emulsified hollandaise here, the pickles and onion juice risk thinning or splitting it.
• No quantities are givenThe entry assumes you have already made the base sauce. Add the garnishes a tablespoon at a time, tasting as you go; any yield figure is guesswork, since the recipe states none.
• Heat limitIf the base sauce contains egg yolk, keep it below a simmer once the yolk is in — roughly 160-175F. Boiling curdles it, and the added vinegar from pickles makes curdling more likely, not less.
• Onion juiceA period shortcut for onion flavour without texture: grate a peeled onion on a fine grater and press the pulp through a sieve. A few drops go a long way; it is much stronger than chopped onion.
• Gherkins and mixed picklesThese are packed in vinegar and salt, so add them last and season the sauce afterwards. Chop them fine and drain them, or the sauce will slacken.
• OlivesRead this as brine-cured green olives, pitted and chopped — the canned black olive was not the default. Rinse them if they are very salty.