Why it works: Parsley and pepper match in chemistry and in kitchens. They rank in the top 2% of all ingredient pairs, and 34,122 recipes mention both. Both carry 4'-methylacetophenone, which smells bitter almond. The science ↓
Onion-soup, Paris Fashion
Ingredients
Directions
Make the soup
Mince the onions and fry them in butter over moderate heat, turning until golden.
Add a pinch of sugar and continue frying until nicely colored.
Moisten with the warm consommé and add the parsley and bay leaf.
Let the liquid boil for 8 minutes.
Assemble and serve
Broil thin slices of white bread and layer them in a soup tureen, sprinkling each layer with fine pepper.
Pour the soup over the bread and serve.
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 aroma chemistry they share, and how many recipes mention both.
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Parsley + peppertop 2% of all pairsAroma overlapstrongMentioned together34,122 recipes
Shared aroma: 4'-methylacetophenone (bitter almond).
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Butter + breadtop 7% of all pairsAroma overlapmoderateMentioned together27,232 recipes
Shared aroma: delta-decalactone (sweet, creamy).
-
Onion + parsleytop 9% of all pairsAroma overlapmoderateMentioned together25,843 recipes
Shared aroma: 2,4-decadienal (seaweed).
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Onion + peppertop 11% of all pairsAroma overlapmoderateMentioned together68,474 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Onion + buttertop 15% of all pairsAroma overlapmoderateMentioned together42,912 recipes
Shared aroma: decanal (soap, orange peel).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Portugal onions
- Provide the main body and sweetness of the soup as they caramelize during frying.
- Butter
- Fat that fries the onions and carries flavor, helping them brown evenly.
- White bread
- Soaks up the soup in the tureen, giving the dish a soft, substantial texture.
- Consommé
- Provides the liquid base and savory meaty flavor for the soup.
The step that matters
Frying the onions until golden. Onions that are only pale lack the deep, sweet flavor that browning creates. Slow frying over moderate heat lets sugars caramelize without scorching, and the added sugar helps this color develop.
Flavor stand-ins for the parsley
How well each one fits the dish's main ingredients (onion, butter, sugar, bread, pepper):
- Garlicabout as good a flavor fit
- Cinnamonabout as good a flavor fit
- Parsleythe original
- Thymeabout as good a flavor fit
Fit is the average pairing score against onion, butter, sugar, bread, pepper. Candidates are from the same food group and used in at least 100 recipes. This compares flavor only: it does not check the job the ingredient does in the dish (bulk, moisture, acidity, structure).
“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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