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Boiled Onions

Boiled onions served with a creamy sauce made from butter, flour, milk, and egg yolks.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 11 ingredients
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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 ↓

Boiled Onions

Ingredients

Directions

Prepare the onions

  1. Peel the onions and trim the roots without cutting them.

  2. Cover the onions with salted water and boil for 10 minutes.

  3. Change the water and continue boiling until tender.

  4. Drain the water and cover the onions with hot milk; cook for 5 more minutes.

Make the cream sauce

  1. For the cream sauce, melt the butter in a pan, add the flour, and rub until smooth.

  2. When the mixture is light brown, add the milk and onion broth, stirring until thick.

  3. Season the sauce with salt and pepper.

  4. Just before serving, stir in the beaten egg yolks mixed with water.

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. Butter + flourtop 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).

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

Onions
Form the body of the dish, becoming tender and sweet as they cook.
Butter
Carries fat for the sauce and helps the flour cook into a smooth roux.
All-purpose flour
Thickens the sauce by absorbing liquid as it cooks with the milk.
Milk
Forms the base of the cream sauce, giving it body and richness.
Eggs
Yolks enrich and thicken the sauce, giving it a silky texture.

The step that matters

Stir in the egg yolks just before serving. Egg yolks thicken when heated, but if the sauce is too hot or boils after they are added, they can curdle and turn grainy. Adding them off the heat or at the end keeps the sauce smooth.

Swap the onion

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

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

Fit is the average pairing score against milk, butter, flour, pepper, egg. 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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