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Sauce

Brown Onion Sauce — Piquant

A savory brown onion sauce flavored with vinegar, mustard flour, veal gravy, and Espagnole sauce.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 8 ingredients
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Why it works: Onion and mustard match in chemistry and in kitchens. They rank in the top 6% of all ingredient pairs, and cooks put them together in 9,259 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓

Brown Onion Sauce — Piquant

Ingredients

Directions

  1. Melt butter in a saucepan and lightly fry the chopped onions.

  2. Add vinegar and reduce it to one third.

  3. Stir in mustard flour until well mixed.

  4. Slowly add veal gravy and Espagnole sauce while stirring.

  5. Let the sauce boil slowly for 25 minutes.

  6. Season with salt and pepper, then strain through a fine sieve.

  7. Keep the sauce warm until ready to serve.

Recipe from a historical cookbook (Internet Archive).

Transcribed from a scanned cookbook and modernised for today's kitchens. Where the book gave no heat or time, or said "a moderate oven", the temperatures and times here may be modern equivalents rather than the book's own figures.

Explore the science

The flavor team

The pairs that carry this dish. Each one is judged two ways: how much their aromas overlap, and how often cooks already put them together.

  1. Onion + mustardtop 6% of all pairs
    Smell alikestrong
    Cooked together9,259 recipes

    Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).

  2. Vinegar + mustardtop 7% of all pairs
    Smell alikemoderate
    Cooked together14,067 recipes

    Shared aroma: isobutyraldehyde (malty, green).

  3. Mustard + peppertop 9% of all pairs
    Smell alikemoderate
    Cooked together15,430 recipes

    Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).

  4. Onion + peppertop 11% of all pairs
    Smell alikemoderate
    Cooked together68,474 recipes

    Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).

  5. Butter + flourtop 12% of all pairs
    Smell alikelow
    Cooked together124,287 recipes

    Shared aroma: isobutyraldehyde (malty, green).

Butter and flour barely smell alike, yet cooks put them together in 124,287 recipes: they work on texture and structure more than aroma.

Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs

What each ingredient does

Red onions
Caramelised sweetness and body as the main flavour base of the sauce.
Vinegar
Adds acidity that sharpens the sauce and balances the sweetness of the onions.
Mustard flour
Adds pungency and helps thicken the sauce as it is stirred in.
Veal gravy
Contributes savoury meaty depth and liquid body to the sauce.
Espagnole sauce
Provides a rich, thickened brown sauce base that gives the sauce its body and colour.

The step that matters

Let the sauce boil slowly for 25 minutes. A gentle simmer lets the liquid reduce and the flavours concentrate without scorching the onions or sugars. Boiling too hard can burn the bottom of the pan and make the sauce bitter.

Swap the onion

How well each one fits the dish's main ingredients (butter, vinegar, mustard, flour, veal, sauce, pepper):

  1. Shallotfits better
  2. Horseradishfits better
  3. Capsicumfits better
  4. Onionthe original

Fit is the average pairing score against butter, vinegar, mustard, flour, veal, sauce, pepper. Candidates are from the same food group and used in at least 100 recipes.

“What each ingredient does” and “The step that matters” were written by Claude from this recipe’s own method and reviewed in samples by CompKitchen.

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