Why it works: Onion and pepper are a kitchen classic. They rank in the top 11% of all ingredient pairs, and 68,474 recipes mention both. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓
Onion Soup with Water
Ingredients
Directions
Prepare
Slice the onions.
Place the sliced onions in a saucepan with the grease.
Make the soup
Cook the onions over medium heat, stirring until they are half brown.
Sift in the flour or bread crumbs.
Continue to brown well.
Add the boiling water, salt, pepper, and any cold cooked vegetables.
Cut the bread into small pieces and fry the bread pieces in grease until brown.
Add the fried bread to the soup.
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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Onion + peppertop 11% of all pairsAroma overlapmoderateMentioned together68,474 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Onion + breadtop 15% of all pairsAroma overlapmoderateMentioned together8,676 recipes
Shared aroma: 2,4-decadienal (seaweed).
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Pepper + breadtop 16% of all pairsAroma overlapmoderateMentioned together20,964 recipes
Shared aroma: 2-nonenal (fatty, green).
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Onion + flourtop 17% of all pairsAroma overlapmoderateMentioned together32,460 recipes
Shared aroma: isobutyraldehyde (malty, green).
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Flour + peppertop 19% of all pairsAroma overlapmoderateMentioned together50,459 recipes
Shared aroma: isobutyraldehyde (malty, green).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Onions
- Browning them builds the deep, sweet flavour that gives the soup its character.
- Flour or fine bread crumbs
- Browned with the onions and then simmered in the liquid, it thickens the soup.
- Bread
- Fried until brown, it adds crisp texture and toasted flavour when added to the soup.
The step that matters
Continue to brown well. Browning the onions and flour deeply develops sweet, roasted flavour through the Maillard reaction and caramelisation. Stopping early leaves the soup pale and tasting flat.
“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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