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Onion Sauce

A savory sauce made with onions, flour, milk or broth, butter, pepper, and salt.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 5 ingredients
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Why it works: Pepper and onion are a kitchen classic. They rank in the top 11% of all ingredient pairs, and cooks put them together in 68,474 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓

Onion Sauce

Ingredients

Directions

Prepare the onions

  1. Skin the onions and boil them in plenty of water until soft.

  2. Remove the onions from the water and chop them very finely.

Make the sauce

  1. In a saucepan, make a roux by cooking the flour in a little butter until golden.

  2. Gradually stir in the milk or broth until smooth.

  3. Add the chopped onions and season with pepper and salt.

  4. Serve as required.

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. Pepper + oniontop 11% of all pairs
    Smell alikemoderate
    Cooked together68,474 recipes

    Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).

  2. Flour + milktop 14% of all pairs
    Smell alikelow
    Cooked together78,219 recipes

    Shared aroma: isobutyraldehyde (malty, green).

  3. Flour + oniontop 17% of all pairs
    Smell alikemoderate
    Cooked together32,460 recipes

    Shared aroma: isobutyraldehyde (malty, green).

  4. Flour + peppertop 19% of all pairs
    Smell alikemoderate
    Cooked together50,459 recipes

    Shared aroma: isobutyraldehyde (malty, green).

  5. Milk + oniontop 20% of all pairs
    Smell alikemoderate
    Cooked together13,418 recipes

    Shared aroma: hexanal (green, grassy).

Flour and milk barely smell alike, yet cooks put them together in 78,219 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

Onions
Softened by boiling, then chopped, they give the sauce its body and sweet flavour.
Flour
Forms a roux with butter that thickens the liquid into a smooth sauce.
Milk or broth
Forms the liquid base of the sauce, which the roux thickens.

The step that matters

Cooking the roux. Flour cooked in butter until golden loses its raw starch taste and thickens the liquid better. Adding the milk or broth gradually while stirring prevents lumps from forming.

Swap the onion

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

  1. Capsicumfits better
  2. Arrowrootfits better
  3. Potatofits better
  4. Onionthe original

Fit is the average pairing score against flour, milk, 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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