Why it works: Onion and pork are a kitchen classic. They rank in the top 10% of all ingredient pairs, and cooks put them together in 18,214 recipes. Both carry 2-isopropyl-3-methoxypyrazine, which smells earthy, pea. The science ↓
Onion Soup
Ingredients
Directions
Prepare the base
Cut the pork into thin slices and fry slowly in a soup kettle.
Once thoroughly fried, add the sliced onions and fry until golden brown, about 30 minutes.
Stir in the flour and cook for an additional 10 minutes, avoiding dark browning.
Simmer and season
Add 1 quart of boiling water and simmer gently for 2 hours (1 hour is sufficient if short on time).
Season with salt and pepper, then add the milk and bring to a boil.
Finish and serve
Strain the soup and stir in the cracker crumbs.
Boil for 3 minutes and serve.
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 + 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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Milk + porktop 12% of all pairsSmell alikemoderateCooked together4,386 recipes
Shared aroma: 4-heptenal (creamy, biscuit).
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Milk + flourtop 14% of all pairsSmell alikelowCooked together78,219 recipes
Shared aroma: isobutyraldehyde (malty, green).
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Pork + peppertop 16% of all pairsSmell alikemoderateCooked together22,121 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Milk and flour barely smell alike, yet cooks put them together in 78,219 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
- Onions
- Browning slowly in fat releases their natural sugars, giving the soup sweetness and depth.
- Flour
- Cooked into the fat, it thickens the soup and gives it body.
- Milk
- Adds creaminess and a soft, rich mouthfeel to the broth.
- Cracker crumbs
- Absorb liquid and add further thickness to the finished soup.
- Fat salt pork
- Its rendered fat carries flavour and cooks the onions, adding savoury richness.
The step that matters
Cook the flour gently. Stirring flour into the fat and cooking it gently builds nutty flavour and full thickening power. If it darkens too far it turns bitter and loses its ability to thicken, so keep it pale and move quickly.
Swap the onion
How well each one fits the dish's main ingredients (milk, flour, pork, pepper):
- Potatofits better
- Capsicumfits better
- Asparagusfits better
- Onionthe original
Fit is the average pairing score against milk, flour, 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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