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Spanish Onions and White Sauce

A dish of boiled onions topped with a white sauce and served on toast.

From an old cookbook · modernised transcription
From a historical cookbook (Internet Archive) · 8 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 ↓

Spanish Onions and White Sauce

Ingredients

Directions

Cook the onions

  1. Boil the onions whole in water for 2 to 2.5 hours until tender.

  2. Drain the onions, reserving the cooking water for soup or stew.

Make the white sauce

  1. In a saucepan, boil the milk with the butter, salt, and pepper.

  2. Thicken the sauce with cornflour, then bring it to a boil again.

Serve

  1. Serve the sauce over the onions on hot slices of toast.

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

    Shared aroma: decanal (soap, orange peel).

  4. Onion + milktop 20% of all pairs
    Smell alikemoderate
    Cooked together13,418 recipes

    Shared aroma: hexanal (green, grassy).

  5. Butter + peppertop 21% of all pairs
    Smell alikemoderate
    Cooked together85,593 recipes

    Shared aroma: trans-2-nonenal (cardboard, fatty).

Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs

What each ingredient does

Onions
Form the main body of the dish, becoming soft and sweet as they cook slowly in water.
Milk
Forms the liquid base of the white sauce, giving it a smooth, creamy texture.
Butter
Adds fat and richness to the white sauce and carries flavour.
Cornflour
Thickens the milk into a smooth sauce as it heats and its starch swells.

The step that matters

Thicken the sauce with cornflour, then bring it to a boil again. Cornflour must be stirred in smoothly and heated so its starch swells and thickens the sauce. Adding it lumpy or without enough heat leaves a grainy or thin sauce.

Swap the onion

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

  1. Potatofits better
  2. Capsicumfits better
  3. Tomatofits about as well
  4. Onionthe original

Fit is the average pairing score against milk, 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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