Why it works: Butter and bread are a kitchen classic. They rank in the top 7% of all ingredient pairs, and cooks put them together in 27,232 recipes. Both carry delta-decalactone, which smells sweet, creamy. The science ↓
Onion Soup
Ingredients
Directions
Melt the butter over medium heat in a stew pan.
Add the sliced onions and sugar, cooking until they turn golden brown.
Pour in the broth and bring to a simmer.
Add the bread slices and cook for a few more minutes.
Stir in the Cognac before serving.
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 + breadtop 7% of all pairsSmell alikemoderateCooked together27,232 recipes
Shared aroma: delta-decalactone (sweet, creamy).
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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 + breadtop 15% of all pairsSmell alikemoderateCooked together8,676 recipes
Shared aroma: 2,4-decadienal (seaweed).
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Butter + sugartop 17% of all pairsSmell alikemoderateCooked together98,233 recipes
Shared aroma: guaiacol (smoky, sweet).
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Sugar + breadtop 32% of all pairsSmell alikelowCooked together8,638 recipes
Shared aroma: 2-nonenal (fatty, green).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Onions
- Provide the bulk of the soup and, when cooked down, its sweet, deep flavor.
- Butter
- Carries fat for cooking the onions and adds rich flavor.
- Sugar
- Helps the onions brown and adds sweetness.
- Broth
- Forms the liquid base of the soup.
- Bread
- Soaks up broth and thickens the soup slightly.
- Cognac
- Adds a warm, aromatic note stirred in at the end.
The step that matters
Cooking the onions to golden brown. Onions need slow, steady browning over medium heat so their natural sugars caramelize and build deep flavor. Rushing with high heat can scorch them and leave a bitter taste.
Swap the onion
How well each one fits the dish's main ingredients (butter, sugar, bread):
- Leekfits better
- Sweet potatofits better
- Capsicumfits better
- Onionthe original
Fit is the average pairing score against butter, sugar, bread. 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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