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Sauce

Plain Onion or Caper Sauce

A sauce made with onions or capers, thickened with flour and stock, seasoned with caper vinegar and salt.

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

  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 sauce

  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.

  3. For a richer sauce, add 1 ounce of butter or use half milk and half stock.

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. Flour + buttertop 12% of all pairs
    Smell alikelow
    Cooked together124,287 recipes

    Shared aroma: isobutyraldehyde (malty, green).

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

    Shared aroma: acetic acid (sour, vinegar).

  5. Onion + buttertop 15% of all pairs
    Smell alikemoderate
    Cooked together42,912 recipes

    Shared aroma: decanal (soap, orange peel).

Flour and butter 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

Flour
Thickens the stock into a smooth sauce as its starch swells when heated.
Stock
Forms the liquid base of the sauce that the flour thickens.
Capers
Add a sharp, briny flavour that defines the Caper Sauce.
Caper vinegar
Adds acidity that brightens the sauce and complements the capers.
Butter
Adds fat for a richer flavour and smoother mouthfeel in the optional version.

The step that matters

Mix the flour with cold water until smooth. Flour added to hot liquid without first being dispersed in cold water clumps into lumps that are hard to remove. Starch must be fully separated before heating so the sauce thickens evenly.

Swap the onion

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

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

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