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Preserve

French Mustard

A mustard condiment made by steeping onion in vinegar, then adding cayenne pepper, salt, sugar, and mustard to thicken.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 6 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 ↓

French Mustard

Ingredients

Directions

Prepare the onion

  1. Slice the onion and cover it with vinegar in a bowl.

  2. After two days, pour off the vinegar.

Make the mustard

  1. Add cayenne pepper, salt, sugar, and enough mustard to thicken.

  2. Set the mixture on the stove until it boils.

  3. Let it cool before using.

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. Pepper + mustardtop 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. Onion + vinegartop 14% of all pairs
    Smell alikemoderate
    Cooked together18,226 recipes

    Shared aroma: acetic acid (sour, vinegar).

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

What each ingredient does

Onion
Softened by vinegar, it adds sharp aroma and body to the mustard.
Good vinegar
Its acidity softens the onion and gives the mustard its tang.
Mustard
Thickens the mixture and supplies the main mustard flavour.
Sugar
Balances the sharpness of the vinegar and mustard with sweetness.

The step that matters

Set the mixture on the stove until it boils. Heat drives off some of the vinegar's sharpness and thickens the mixture, so it should be brought just to a boil rather than left to simmer unchecked or taken off too early.

Swap the onion

How well each one fits the dish's main ingredients (vinegar, pepper, sugar, mustard):

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

Fit is the average pairing score against vinegar, pepper, sugar, mustard. 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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