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Onion Sauce

A creamy sauce made from boiled onions, milk, flour, butter, salt, and pepper.

From an old cookbook · modernised transcription
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Why it works: Milk and butter are a kitchen classic. They rank in the top 7% of all ingredient pairs, and cooks put them together in 81,283 recipes. Both carry (z)-4-heptenal, which smells biscuit, cream. The science ↓

Onion Sauce

Ingredients

Directions

Prepare the onions

  1. Peel the onions and boil them until tender.

  2. Drain and chop the onions finely.

Make the sauce

  1. In a saucepan, heat the milk.

  2. Add the flour and butter to the milk, stirring until combined.

  3. Stir in the chopped onions and season with salt and pepper.

  4. Boil for a few minutes and serve with roast pork.

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. Milk + buttertop 7% of all pairs
    Smell alikemoderate
    Cooked together81,283 recipes

    Shared aroma: (z)-4-heptenal (biscuit, cream).

  2. Onion + peppertop 11% of all pairs
    Smell alikemoderate
    Cooked together68,474 recipes

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

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

    Shared aroma: isobutyraldehyde (malty, green).

  4. Milk + flourtop 14% of all pairs
    Smell alikelow
    Cooked together78,219 recipes

    Shared aroma: isobutyraldehyde (malty, green).

  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

Onions
Provide the main body and sweet flavour of the sauce once chopped and stirred in.
Milk
Forms the liquid base that the sauce is built on.
Flour
Thickens the milk so the sauce becomes smooth and coats the onions.
Butter
Adds richness and helps the flour blend smoothly into the milk.

The step that matters

Adding the flour and butter to the milk. Stirring constantly as the flour and butter are added keeps lumps from forming. Flour needs to be fully dispersed in the warm liquid so starch can hydrate evenly and thicken the sauce smoothly.

Swap the onion

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

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

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