Why it works: Onion and potato are a kitchen classic. They rank in the top 3% of all ingredient pairs, and cooks put them together in 9,023 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓
Onion Soup
Ingredients
Directions
In a saucepan, melt the butter over medium heat.
Add the sliced onions and cook until they are red.
Stir in the flour and cook until it turns red, being careful not to burn it.
Pour in the boiling water, add pepper and salt, and mix well.
Let it boil for one minute, then transfer to a soup kettle and keep warm.
Add the boiling milk to the soup.
Mash the boiled potatoes and gradually mix in some soup until smooth.
Pour the potato mixture into the soup kettle and stir well.
Taste and adjust seasoning with more pepper and salt if needed.
Let it simmer for a few minutes and serve with pieces of toasted bread.
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 + potatotop 3% of all pairsSmell alikemoderateCooked together9,023 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Butter + breadtop 7% of all pairsSmell alikemoderateCooked together27,232 recipes
Shared aroma: delta-decalactone (sweet, creamy).
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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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Potato + peppertop 9% of all pairsSmell alikemoderateCooked together8,305 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Milk + potatotop 9% of all pairsSmell alikemoderateCooked together3,611 recipes
Shared aroma: (e,z)-2,6-nonadienal (cucumber, melon).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
Swap the onion
How well each one fits the dish's main ingredients (milk, potato, butter, pepper, bread):
- Capsicumfits better
- Tomatofits better
- Asparagusfits about as well
- Onionthe original
Fit is the average pairing score against milk, potato, butter, pepper, bread. Candidates are from the same food group and used in at least 100 recipes.
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