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Sauce

Plain Onion or Caper Sauce

A simple sauce made from onions or capers, thickened with flour and stock, seasoned with salt.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 6 ingredients
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Why it works: Capers and flour match in chemistry and in kitchens. They rank in the top 6% of all ingredient pairs, and cooks put them together in 1,024 recipes. Both carry isobutyraldehyde, which smells malty, green. The science ↓

Plain Onion or Caper Sauce

Ingredients

Directions

Make the sauce

  1. Mix the flour with a little cold water until smooth.

  2. Gradually add the stock, stirring well.

  3. Pour the mixture into a small saucepan and stir until it boils, adding salt to taste.

Finish the sauces

  1. For Caper Sauce, cut the capers in half and add the vinegar.

  2. For Onion Sauce, boil the onions in two waters until soft, then chop finely and stir into the sauce.

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. Capers + flourtop 6% of all pairs
    Smell alikestrong
    Cooked together1,024 recipes

    Shared aroma: isobutyraldehyde (malty, green).

  2. Onion + caperstop 7% of all pairs
    Smell alikestrong
    Cooked together1,381 recipes

    Shared aroma: coumarin (sweet, hay).

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

    Shared aroma: acetic acid (sour, vinegar).

  4. Capers + vinegartop 16% of all pairs
    Smell alikemoderate
    Cooked together1,453 recipes

    Shared aroma: isobutyraldehyde (malty, green).

  5. Onion + flourtop 17% of all pairs
    Smell alikemoderate
    Cooked together32,460 recipes

    Shared aroma: isobutyraldehyde (malty, green).

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

What each ingredient does

Flour
Starch thickens the stock into a smooth sauce when it heats and boils.
Stock
Forms the liquid base of the sauce and carries its savoury flavour.
Capers
Add a sharp, salty flavour that cuts through the richness of the sauce.
Caper vinegar
Adds acidity that brightens the caper flavour.

The step that matters

Stirring the stock into the flour. Adding the liquid gradually while stirring lets the flour disperse evenly. Adding it all at once makes lumps that are hard to remove. The sauce must then reach a boil so the starch fully thickens.

Swap the onion

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

  1. Shallotfits better
  2. Mustardfits better
  3. Arrowrootfits better
  4. Onionthe original

Fit is the average pairing score against capers, vinegar, flour. 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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