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Onion Sauce

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

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 6 ingredients
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Why it works: Butter and milk 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. Soak the onions overnight in boiling water.

  2. Boil the soaked onions in boiling water for 30 minutes.

  3. Chop the boiled onions finely and cover them with milk to preserve their color.

Make the sauce

  1. Melt the butter in a small saucepan, add the flour, then pour in the onions and milk mixture.

  2. Bring to a boil, add salt and pepper, and boil for 2 minutes before serving.

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. Butter + milktop 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. Butter + flourtop 12% of all pairs
    Smell alikelow
    Cooked together124,287 recipes

    Shared aroma: isobutyraldehyde (malty, green).

  4. Flour + milktop 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).

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

Spanish onions
Provide the bulk and sweet, savory flavor that forms the body of the sauce.
Butter
Adds fat and richness, carrying flavor through the sauce.
Flour
Thickens the milk and onion mixture into a smooth sauce as it heats.
Milk
Forms the liquid base of the sauce and adds creaminess.

The step that matters

Bring to a boil and boil for 2 minutes. Flour needs to reach a boil and simmer briefly to fully swell and thicken the liquid. Stopping early leaves the sauce thin and possibly tasting of raw starch.

Swap the onion

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

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

Fit is the average pairing score against butter, 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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