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
Make the soup
Melt the butter in a saucepan over medium heat.
Add the chopped onions and stir continuously to prevent burning.
Cook until the onions are soft and pale golden in color.
Pour in the fresh milk and gently bring to a boil.
Serve
Place the crisped, buttered bread in a tureen and pour the soup over it.
Serve immediately.
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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Butter + milktop 7% of all pairsSmell alikemoderateCooked together81,283 recipes
Shared aroma: (z)-4-heptenal (biscuit, cream).
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Milk + breadtop 11% of all pairsSmell alikemoderateCooked together11,466 recipes
Shared aroma: 2-undecenal (sweet).
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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).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Onions
- Provide the main flavor and sweetness as they soften and turn golden.
- Butter
- Carries fat for cooking the onions and adds richness to the soup.
- Fresh milk
- Forms the creamy liquid base of the soup.
- Stale bread
- Soaks up the soup and gives the dish body and texture when served.
The step that matters
Stir the onions continuously while they cook. Onions contain sugars that scorch quickly over direct heat. Constant stirring keeps them cooking evenly so they turn golden and sweet rather than burnt and bitter.
Swap the onion
How well each one fits the dish's main ingredients (butter, milk, bread):
- Potatofits better
- Tomatofits better
- Asparagusfits about as well
- Onionthe original
Fit is the average pairing score against butter, milk, 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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