Why it works: Pepper and clove match in chemistry and in kitchens. They rank in the top 5% of all ingredient pairs, and cooks put them together in 17,451 recipes. Both carry ethyl octanoate, which smells fruity, wine. The science ↓
Brown Onion Soup
Ingredients
Directions
Prepare the onions
Skin and slice the onions.
Fry the sliced onions in butter until brown and tender.
Drain the fried onions on a sieve.
Make the soup
In a pot, combine the drained onions with boiling water and boil for 1 hour, stirring often.
Add pepper and salt to taste.
Rub the crumbs of the loaf through a colander and add them to the soup, stirring well to avoid lumps.
Boil the soup for an additional 2 hours.
Add cloves if desired.
Finish and serve
Before serving, beat the egg yolks with vinegar and a little soup, then gradually stir the mixture into the pot while stirring continuously.
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 + clovetop 5% of all pairsSmell alikestrongCooked together17,451 recipes
Shared aroma: ethyl octanoate (fruity, wine).
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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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Onion + clovetop 13% of all pairsSmell alikemoderateCooked together16,901 recipes
Shared aroma: 2-nonanone (fruity, floral).
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Onion + vinegartop 14% of all pairsSmell alikemoderateCooked together18,226 recipes
Shared aroma: acetic acid (sour, vinegar).
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Pepper + vinegartop 14% of all pairsSmell alikemoderateCooked together27,814 recipes
Shared aroma: 4'-methylacetophenone (bitter almond).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Spanish onions
- Provide the main body and sweet, savoury flavour of the soup as they soften and brown.
- Butter
- Fat that browns the onions, adding richness and deeper flavour.
- Penny loaf crumbs
- Bread thickens the soup and gives it a fuller, smoother body.
- Egg yolks
- Enrich and thicken the soup as they gently set when stirred into the hot liquid.
- Vinegar
- Adds acidity that brightens the sweet onion flavour and balances the richness of the yolks.
The step that matters
Adding the egg yolk mixture. Egg yolks can scramble if they meet very hot liquid directly. Tempering them with a little soup first, then stirring gradually and continuously, helps them blend in smoothly and thicken the soup without curdling.
Swap the clove
The recipe marks clove as optional. How well each one fits the dish's main ingredients (onion, butter, pepper, egg, vinegar):
- Parsleyfits better
- Tarragonfits better
- Garlicfits better
- Clovethe original
Fit is the average pairing score against onion, butter, pepper, egg, vinegar. 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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