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Dessert

French Mustard

A mustard condiment made with onion, vinegar, spices, sugar, and mustard.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 7 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

Soak the onion

  1. Slice the onion and place it in a bowl. Cover with vinegar and let it sit for two days.

  2. After two days, pour off the vinegar.

Make the mustard

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

  2. Mix well, then heat on the stove and stir until it boils.

  3. Allow to 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

Mustard
Provides the main sharp flavour and, with enough added, thickens the mixture.
Vinegar
Adds acidity and draws flavour out of the onion as it soaks.
Onion
Contributes savoury body and aroma that softens during the long soak.
Sugar
Adds sweetness that balances the sharpness of the vinegar and mustard.

The step that matters

Heating until it boils. Mustard's sharp heat comes from compounds that form when ground mustard meets liquid and fade with prolonged heat. Stirring until it boils sets the mixture, but overheating can dull the pungency you want.

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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