Why it works: Pepper and onion are a kitchen classic. They rank in the top 11% of all ingredient pairs, and cooks put them together in 68,474 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓
Split-pea or Bean Soup
Ingredients
Directions
Prepare the peas
Soak the split peas or beans overnight in 3 quarts of cold water.
In a saucepan, combine the soaked peas or beans with 2 quarts of water and the ham bone, if using.
Optionally, boil an onion with the peas or beans for added flavor.
Cook and strain
Simmer for 4 to 5 hours, adding more water if necessary, until the peas or beans are soft.
Pass the mixture through a sieve.
Add enough stock, milk, or water to achieve a creamy consistency.
Return the soup to the saucepan.
Finish and serve
Prepare a roux by cooking the butter and flour together.
Dilute the roux with a little soup before adding it to the pot to keep the particles suspended.
Season with salt and pepper.
Serve with croutons on top.
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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Pepper + oniontop 11% of all pairsSmell alikemoderateCooked together68,474 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Butter + flourtop 12% of all pairsSmell alikelowCooked together124,287 recipes
Shared aroma: isobutyraldehyde (malty, green).
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Peas + oniontop 13% of all pairsSmell alikemoderateCooked together5,460 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Sugar + flourtop 15% of all pairsSmell alikemoderateCooked together92,116 recipes
Shared aroma: phenylacetaldehyde (hawthorne, honey).
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Butter + oniontop 15% of all pairsSmell alikemoderateCooked together42,912 recipes
Shared aroma: decanal (soap, orange peel).
Butter and flour barely smell alike, yet cooks put them together in 124,287 recipes: they work on texture and structure more than aroma.
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Split peas or dried beans
- Break down during long simmering to form the thick body of the soup.
- Butter
- Carries flavor and adds richness when cooked into the roux.
- Flour
- Thickens the soup with butter as a roux, giving it a smoother body.
- Sugar
- Adds a small amount of sweetness that balances the savory peas.
The step that matters
Adding the roux. Flour clumps if added raw or undiluted. Diluting the roux with a little hot soup first lets the starch disperse evenly, so the thickening stays smooth rather than lumpy.
Swap the onion
The recipe marks onion as optional. How well each one fits the dish's main ingredients (peas, butter, sugar, flour, pepper, ham):
- Shallotfits better
- Asparagusfits better
- Leekfits better
- Onionthe original
Fit is the average pairing score against peas, butter, sugar, flour, pepper, ham. 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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