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
Make the stock
In a large pot, boil 4 quarts of water with the veal, whole white pepper, and mace until the meat is tender and leaves the bone.
Strain the stock and set it aside.
Prepare the onions
The next day, boil the onions in milk and water until tender enough to pulp through a sieve.
Finish the soup
Remove the fat from the top of the stock, bring it to a boil, and add the onions.
Mix in the butter and sifted rice flour, and season with salt.
Gently boil for 30 minutes, stirring constantly.
Just before serving, stir in the rich cream.
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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Milk + buttertop 7% of all pairsSmell alikemoderateCooked together81,283 recipes
Shared aroma: (z)-4-heptenal (biscuit, cream).
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Milk + ricetop 7% of all pairsSmell alikemoderateCooked together7,374 recipes
Shared aroma: 2-nonenal (fatty, green).
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Onion + ricetop 9% of all pairsSmell alikemoderateCooked together10,433 recipes
Shared aroma: 2,4-decadienal (seaweed).
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White pepper + macetop 9% of all pairsSmell alikemoderateCooked together1,695 recipes
Shared aroma: myrcene (balsamic, herbaceous).
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Butter + flourtop 12% of all pairsSmell alikelowCooked together124,287 recipes
Shared aroma: isobutyraldehyde (malty, green).
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
- Knuckle of veal
- Releases gelatin and flavor into the stock, giving the soup body and richness.
- Spanish onions
- Cooked soft and pulped, they provide the main body, sweetness and flavor of the soup.
- Fresh butter
- Adds fat for a rich mouthfeel and carries flavor through the soup.
- Rice flour
- Starch that thickens the soup as it simmers, giving it a smooth body.
- Rich cream
- Adds fat and creaminess, softening the flavor and smoothing the texture.
The step that matters
Stirring while the soup gently boils. Once the flour is in, the starch can settle and scorch on the bottom of the pot, and constant stirring keeps it smooth and evenly thickened.
Swap the white pepper
How well each one fits the dish's main ingredients (veal, mace, onion, milk, butter, rice, flour):
- Nutmegfits better
- Cinnamonfits better
- Turmericfits better
- White pepperthe original
Fit is the average pairing score against veal, mace, onion, milk, butter, rice, flour. 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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