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Hot Mustard Sauce

A quick sauce of butter, flour, boiling water, mustard, pickles or capers, salt, and pepper for boiled fish.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 7 ingredients
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Why it works: Mustard and capers match in chemistry and in kitchens. They rank in the top 1% of all ingredient pairs, and cooks put them together in 624 recipes. Both carry coumarin, which smells sweet, hay. The science ↓

Hot Mustard Sauce

Ingredients

Directions

Make the sauce

  1. In a saucepan over medium heat, melt the butter and stir in the flour.

  2. Gradually add the boiling water while stirring continuously.

  3. Mix in the mustard, chopped pickles or capers, salt, and pepper.

  4. Continue stirring until the sauce boils, then cook for 2 minutes.

Serve

  1. Serve the sauce with boiled fish.

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. Mustard + caperstop 1% of all pairs
    Smell alikestrong
    Cooked together624 recipes

    Shared aroma: coumarin (sweet, hay).

  2. Flour + caperstop 6% of all pairs
    Smell alikestrong
    Cooked together1,024 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. Butter + flourtop 12% of all pairs
    Smell alikelow
    Cooked together124,287 recipes

    Shared aroma: isobutyraldehyde (malty, green).

  5. Capers + peppertop 12% of all pairs
    Smell alikemoderate
    Cooked together2,088 recipes

    Shared aroma: coumarin (sweet, hay).

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

Butter
Melted fat that coats the flour and gives the sauce richness.
Flour
Starch that thickens the liquid into a smooth, body-rich sauce when it boils.
Prepared mustard
Provides the sharp, hot flavour that defines the sauce.
Pickles or capers
Adds acidity and a tangy bite that balances the richness.

The step that matters

Adding the boiling water gradually. Pouring the water in slowly while stirring keeps the flour smooth. Adding it all at once can trap dry lumps that stay in the sauce.

Swap the mustard

How well each one fits the dish's main ingredients (butter, flour, capers, pepper):

  1. Shallotfits better
  2. Chivefits about as well
  3. Arrowrootfits about as well
  4. Mustardthe original

Fit is the average pairing score against butter, flour, capers, 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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