Why it works: Onion and peas are a kitchen classic. They rank in the top 13% of all ingredient pairs, and cooks put them together in 5,460 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓
Made Without Meat
Ingredients
Directions
Prepare the soup
Melt the butter in a soup pot over medium heat.
Slice the onions.
Add the sliced onions to the pot and fry until golden brown, stirring constantly.
Add the cold water and split peas to the pot; bring to a boil.
Reduce heat and simmer for 4 hours.
Finish and serve
Mash the soup with a potato masher.
Strain the mashed soup through a colander into a tureen.
Serve with tomato ketchup on the side, if desired.
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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Onion + peastop 13% of all pairsSmell alikemoderateCooked together5,460 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Butter + oniontop 15% of all pairsSmell alikemoderateCooked together42,912 recipes
Shared aroma: decanal (soap, orange peel).
-
Butter + peastop 16% of all pairsSmell alikemoderateCooked together4,887 recipes
Shared aroma: trans-2-nonenal (cardboard, fatty).
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Onion + coffeetop 22% of all pairsSmell alikemoderateCooked together232 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Butter + coffeetop 23% of all pairsSmell alikemoderateCooked together2,442 recipes
Shared aroma: 2-furfurylthiol (coffee, roasted).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Butter
- Adds fat that carries flavor and helps the onions brown.
- Onions
- Browning in the fat builds sweet, savory depth into the soup.
- Split peas
- Break down during long simmering to thicken the soup and give it body.
The step that matters
Frying the onions until golden brown. Stirring constantly keeps the onions from scorching, while browning creates savory, caramelized flavor that the finished soup depends on. Burnt onions taste bitter and cannot be fixed later.
Swap the peas
How well each one fits the dish's main ingredients (butter, onion, coffee):
- Cocoafits better
- Peanutfits better
- Hazelnutfits better
- Peasthe original
Fit is the average pairing score against butter, onion, coffee. 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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