Why it works: Pepper and lemon match in chemistry and in kitchens. They rank in the top 3% of all ingredient pairs, and cooks put them together in 27,047 recipes. Both carry trans-2-nonenal, which smells cardboard, fatty. The science ↓
Onion Sauce
Ingredients
Directions
Prepare the onions
Blanch the onions in cold water, then bring to a boil.
Drain and place in fresh boiling water; boil until tender, about 1 hour.
Chop the onions finely and add to the white sauce.
Make the sauce
Melt half the butter in a small saucepan, add the flour, and blend well.
Stir in the water gradually and boil for 3 minutes.
Remove from heat and mix in the remaining butter in small pieces, ensuring each piece is fully incorporated before adding the next.
Do not allow the sauce to boil after adding the butter.
Season with salt and pepper, and add lemon juice if using for fish or veal.
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.
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Pepper + lemontop 3% of all pairsSmell alikestrongCooked together27,047 recipes
Shared aroma: trans-2-nonenal (cardboard, fatty).
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Onion + peppertop 11% of all pairsSmell alikemoderateCooked together68,474 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Butter + flourtop 12% of all pairsSmell alikelowCooked together124,287 recipes
Shared aroma: isobutyraldehyde (malty, green).
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Sauce + buttertop 15% of all pairsSmell alikelowCooked together15,338 recipes
Shared aroma: ethanol (alcoholic, ethereal).
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Onion + buttertop 15% of all pairsSmell alikemoderateCooked 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
- Become tender and sweet, and give the sauce its body and flavour.
- White sauce
- Forms the creamy base that carries the onions.
- Butter
- Adds richness and a smooth, glossy finish to the sauce.
- Flour
- Thickens the sauce by absorbing liquid and swelling when heated.
The step that matters
Adding the butter off the heat. Once the butter is stirred in, boiling can split the emulsion, making the sauce greasy and grainy. Removing it from the heat and adding butter in small pieces keeps the sauce smooth and glossy.
Swap the lemon
The recipe marks lemon as optional. How well each one fits the dish's main ingredients (onion, sauce, butter, flour, pepper):
- Avocadofits better
- Limefits about as well
- Lemonthe original
- Mangofits about as well
Fit is the average pairing score against onion, sauce, butter, flour, 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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