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
Peel the onions and boil them in plenty of water until soft.
Strain the onions and chop them finely.
Season with salt and pepper.
Stir the chopped onions into melted butter.
Optional: Add milk for a richer, whiter sauce.
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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Butter + milktop 7% of all pairsSmell alikemoderateCooked together81,283 recipes
Shared aroma: (z)-4-heptenal (biscuit, cream).
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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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Onion + buttertop 15% of all pairsSmell alikemoderateCooked together42,912 recipes
Shared aroma: decanal (soap, orange peel).
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Onion + milktop 20% of all pairsSmell alikemoderateCooked together13,418 recipes
Shared aroma: hexanal (green, grassy).
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Pepper + buttertop 21% of all pairsSmell alikemoderateCooked 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
- Provide the main body and sweet, mellow flavour of the sauce once softened and chopped.
- Butter
- Carries flavour and adds richness and a smooth, silky mouthfeel to the onions.
- Milk
- Adds richness and lightens the colour of the sauce, making it creamier and whiter.
The step that matters
Boil the onions until soft. Onions that are not cooked through stay firm and sharp-tasting, and the sauce will be grainy rather than smooth. Boiling until fully soft breaks down their cell walls so they blend into a silky sauce.
Swap the onion
How well each one fits the dish's main ingredients (pepper, butter, milk):
- Potatofits better
- Capsicumfits better
- Tomatofits about as well
- Onionthe original
Fit is the average pairing score against pepper, butter, milk. 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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