Why it works: Milk and butter are a kitchen classic. They rank in the top 7% of all ingredient pairs, and cooks put them together in 81,283 recipes. Both carry (z)-4-heptenal, which smells biscuit, cream. The science ↓
Onion Soup
Ingredients
Directions
Prepare the onions
Put the butter in a frying pan.
Cut the onions into thin slices and drop them into the butter.
Stir until they begin to cook; then cover tightly and set back where they will simmer, but not burn, for half an hour.
Make the soup
Put the milk on to boil, then add the dry flour to the onions and stir constantly for three minutes over the fire.
Turn the mixture into the milk and cook fifteen minutes.
Rub the soup through a strainer, return to the fire, season with salt and pepper.
Beat the yolks of the eggs well, add the cream to them and stir into the soup.
Cook three minutes, stirring constantly.
If you have no cream, use milk, in which case add a tablespoonful of butter at the same time.
Serve
Pour over fried croutons in a soup tureen.
Nutrition, whole recipe (rough)
What these numbers assume: 7 portions
| Ingredient | Portion assumed | kcal |
|---|---|---|
| Milk | 1 cup (244ml) whole | 149 |
| Butter | 1 tbsp (14g) | 102 |
| Egg | 1 large egg (50g) | 78 |
| Cream | 1 tbsp (15ml) heavy | 51 |
| Onion | 1 medium (110g) | 44 |
| Black Pepper | 1 tsp ground (2.3g) | 6 |
| Salt | 1 tsp (6g) | 0 |
One typical portion per ingredient; the recipe's quantities are not counted. A rough guide only, not for medical or dietary planning.
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. See the original page.
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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Milk + buttertop 7% of all pairsSmell alikemoderateCooked together81,283 recipes
Shared aroma: (z)-4-heptenal (biscuit, cream).
-
Butter + creamtop 8% of all pairsSmell alikemoderateCooked together41,516 recipes
Shared aroma: delta-dodecalactone (sweet, creamy).
-
Onion + peppertop 11% of all pairsSmell alikemoderateCooked together68,474 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
-
Butter + oniontop 15% of all pairsSmell alikemoderateCooked together42,912 recipes
Shared aroma: decanal (soap, orange peel).
-
Butter + eggtop 17% of all pairsSmell alikemoderateCooked together118,967 recipes
Shared aroma: decanal (soap, orange peel).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Onions
- Soften slowly in butter, adding sweetness and deep savory flavor to the soup.
- Butter
- Carries flavor and adds richness as it cooks the onions gently.
- Milk
- Forms the liquid base that gives the soup its body.
- Cream
- Adds richness and a smoother, silkier texture.
- Eggs
- Yolks thicken the soup and add richness when heated gently.
The step that matters
Adding the egg yolks and cream. Egg yolks thicken when heated gently but scramble if they get too hot. Beating them well and stirring constantly while cooking keeps the soup smooth and evenly thickened.
Swap the onion
How well each one fits the dish's main ingredients (milk, butter, cream, egg, pepper):
- Potatofits better
- Capsicumfits better
- Asparagusfits better
- Onionthe original
Fit is the average pairing score against milk, butter, cream, egg, 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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