Why it works: Milk and butter are a kitchen classic. They rank in the top 7% of all ingredient pairs, and cooks put them together in 81,283 recipes. Both carry (z)-4-heptenal, which smells biscuit, cream. The science ↓
Split Pea Soup
Ingredients
Directions
Prepare
Pick over and wash the split peas, then soak them in plenty of cold water overnight.
In the morning, drain the peas and place them in a kettle with 2 quarts of cold water, salt pork, and sliced onion.
Cook and strain
Cook slowly for 4 to 5 hours, stirring frequently to prevent burning, until the peas are very soft.
Rub the cooked peas through a sieve back into the kettle and bring to a boil.
Thicken and serve
Beat the butter and flour together, thin with a little boiling soup, and stir into the soup.
Season with salt and pepper, add the milk, and serve when the soup boils.
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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Milk + buttertop 7% of all pairsSmell alikemoderateCooked together81,283 recipes
Shared aroma: (z)-4-heptenal (biscuit, cream).
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Onion + porktop 10% of all pairsSmell alikemoderateCooked together18,214 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Onion + peppertop 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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Milk + porktop 12% of all pairsSmell alikemoderateCooked together4,386 recipes
Shared aroma: 4-heptenal (creamy, biscuit).
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
- Break down during long cooking to give the soup its body and thick texture.
- Salt pork
- Releases fat and savory flavor into the water as it simmers with the peas.
- Butter
- Enriches the soup with fat and flavor, and helps the flour blend smoothly.
- Flour
- Thickens the soup as its starch swells in the hot liquid.
- Milk
- Adds creaminess and mild sweetness, softening the soup's flavor.
The step that matters
Thinning the butter and flour mixture. Adding flour directly to hot soup forms lumps, because starch clumps before it disperses. Mixing it with butter and a little boiling soup first lets the starch hydrate evenly, giving a smooth, uniformly thickened result.
Swap the peas
How well each one fits the dish's main ingredients (milk, butter, flour, onion, pork, pepper):
- Beansfits better
- Sesamefits better
- Chestnutfits better
- Peasthe original
Fit is the average pairing score against milk, butter, flour, onion, pork, pepper. 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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