Name: Boiled Onions in White Sauce
Ingredients: 4 medium onions; 2 teaspoons coarse sea salt; 1 pint sweet milk; 1 tablespoon butter; 1 tablespoon all-purpose flour; 1 teaspoon salt; ¼ teaspoon white pepper

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 in White Sauce

Ingredients

Directions

Prepare the onions

Peel the onions.
Cut off the roots.
Place the onions in cold water.
Drain the onions.
Place the onions in a saucepan with boiling water to cover.
Add 2 teaspoons of salt for each quart of water.
Boil for 10 minutes with the cover partially off.
Drain the water.

Make the white sauce

Cover the onions with 1 pint of hot sweet milk.
Simmer for 30 minutes.
In a bowl, beat together 1 tablespoon of butter and 1 tablespoon of flour.
Add 1 teaspoon of salt and ¼ teaspoon of white pepper.
Gradually beat in about ½ cup of the milk from the onions.
When smooth, stir the mixture into the onions and milk.
Cook for an additional 10 minutes.

Serve

Serve.

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.

Milk + buttertop 7% of all pairs

Smell alikemoderate

Cooked together81,283 recipes

Shared aroma: (z)-4-heptenal (biscuit, cream).
Butter + flourtop 12% of all pairs

Smell alikelow

Cooked together124,287 recipes

Shared aroma: isobutyraldehyde (malty, green).
Milk + flourtop 14% of all pairs

Smell alikelow

Cooked together78,219 recipes

Shared aroma: isobutyraldehyde (malty, green).
Onion + buttertop 15% of all pairs

Smell alikemoderate

Cooked together42,912 recipes

Shared aroma: decanal (soap, orange peel).
Onion + flourtop 17% of all pairs

Smell alikemoderate

Cooked together32,460 recipes

Shared aroma: isobutyraldehyde (malty, green).

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: Become sweet and tender during boiling and simmering, giving the sauce its body and flavor.
Sweet milk: Forms the liquid base of the sauce, carrying the onion flavor and thickening when heated.
Butter: Cooked with flour to form a roux that thickens the sauce smoothly and adds richness.
All-purpose flour: Thickens the sauce as its starch swells in the hot milk, forming a smooth white sauce.

The step that matters

Stirring the roux mixture into the hot onions and milk. Adding the flour and butter mixture gradually and beating it smooth before stirring it in prevents lumps, because flour starch clumps if it hits hot liquid all at once.

Swap the white pepper

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

Cinnamonfits better
Capersfits better
Garlicfits better
White pepperthe original

Fit is the average pairing score against onion, milk, butter, flour. 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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Boiled Onions in White Sauce