Why it works: Cream and butter are a kitchen classic. They rank in the top 8% of all ingredient pairs, and cooks put them together in 41,516 recipes. Both carry delta-dodecalactone, which smells sweet, creamy. The science ↓
Onion Soup
Ingredients
Directions
Prepare the onions
Combine the chopped onions and 1 quart of cold water in a stew-pan and bring to a boil.
Drain the liquid and return the onions to the pan.
Pour 2 quarts of boiling water over the onions.
Cook and finish
Cook until very tender, adding 1 tablespoon of salt.
Stir in 1 cup of rich cream and bring to a boil.
Remove from heat.
Mix in 2 egg yolks, a generous lump of butter mixed with a little flour, a dash of pepper, and a pinch of sugar.
Let it bubble and serve hot.
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.
-
Cream + buttertop 8% of all pairsSmell alikemoderateCooked together41,516 recipes
Shared aroma: delta-dodecalactone (sweet, creamy).
-
Cream + sugartop 9% of all pairsSmell alikemoderateCooked together43,450 recipes
Shared aroma: 2,3-butanedione (butter, sweet).
-
Onion + peppertop 11% of all pairsSmell alikemoderateCooked together68,474 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
-
Butter + flourtop 12% of all pairsSmell alikelowCooked together124,287 recipes
Shared aroma: isobutyraldehyde (malty, green).
-
Flour + sugartop 15% of all pairsSmell alikemoderateCooked together92,116 recipes
Shared aroma: phenylacetaldehyde (hawthorne, honey).
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
- Onions
- Provide the main body and sweet, savoury flavour of the soup as they cook down until tender.
- Rich cream
- Adds richness and a smooth, velvety texture to the soup.
- Egg yolks
- Thicken the soup and add richness when mixed in off the heat.
- Butter
- Adds fat and richness, and with flour helps thicken the soup.
- Flour
- Thickens the butter mixture so it blends smoothly into the soup.
The step that matters
Mix in the egg yolks after removing from heat. Egg yolks thicken when heated but can scramble if they get too hot. Removing the pan from heat before adding them lets them thicken the soup gently and smoothly.
Swap the onion
How well each one fits the dish's main ingredients (cream, egg, butter, flour, pepper, sugar):
- Leekfits better
- Chivefits better
- Spinachfits better
- Onionthe original
Fit is the average pairing score against cream, egg, butter, flour, pepper, sugar. 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.
More onion soup recipes
You might also like
The free Flavor Lab newsletter: one surprising pairing a week and the molecular reason it works, in 60 seconds. No spam, unsubscribe anytime.
Prefer an account? Create a free account to save pairings and unlock the full chemistry.
Tomato Soup526 recipes
Brown Bread461 recipes
Mutton Broth292 recipes
Yorkshire Pudding264 recipes