Why it works: Gruyere cheese and parmesan cheese match in chemistry and in kitchens. They rank in the top 1% of all ingredient pairs, and cooks put them together in 152 recipes. Both carry ethyl 2-methylbutyrate, which smells fruity, apple. The science ↓
Onion Soup with Cheese
Ingredients
Directions
Make the soup
Melt the butter in a saucepan over low heat.
Cut the onions into thin slices and blanch them in boiling water.
Add the onions to the hot butter, stirring gently without browning.
Sprinkle the flour over the onions and stir with a wooden spoon.
Add the water or white stock and season with salt and pepper.
Let it boil briefly.
Assemble and serve
Cut the stale bread into thin slices and place them in a tureen.
Mix the Gruyere and Parmesan cheeses together and layer some on the bread.
Pour some of the soup over the bread.
Add another layer of bread sprinkled with cheese and pour in the remaining soup.
Let it stand for 1 hour, keeping the tureen very hot.
For a richer soup, add ½ pint of boiling cream before serving.
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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Gruyere cheese + parmesan cheesetop 1% of all pairsSmell alikestrongCooked together152 recipes
Shared aroma: ethyl 2-methylbutyrate (fruity, apple).
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Butter + breadtop 7% of all pairsSmell alikemoderateCooked together27,232 recipes
Shared aroma: delta-decalactone (sweet, creamy).
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Butter + parmesan cheesetop 9% of all pairsSmell alikemoderateCooked together4,163 recipes
Shared aroma: guaiacol (smoky, sweet).
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Butter + gruyere cheesetop 9% of all pairsSmell alikemoderateCooked together323 recipes
Shared aroma: gamma-decalactone (peach, creamy).
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Onion + peppertop 11% of all pairsSmell alikemoderateCooked together68,474 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Onions
- Soften and sweeten as they cook slowly in butter, forming the body of the soup.
- Butter
- Carries the onions' flavour and enriches the soup with fat, helping it brown gently.
- Flour
- Thickens the stock so the soup has a fuller, smoother body.
- Stale bread
- Soaks up the soup and holds the layers together, giving a bread-and-soup texture.
- Gruyere and parmesan cheeses
- Melt into the soup and bread, adding savoury richness and a stringy, browned topping.
The step that matters
Adding the onions to the butter without browning. Onions cooked gently in butter release their sugars slowly and turn sweet. If they brown too fast, they turn bitter and darken the soup's flavour and colour.
Swap the onion
How well each one fits the dish's main ingredients (butter, flour, pepper, bread, gruyere cheese, parmesan cheese):
- Potatofits better
- Spinachfits better
- Tomatofits better
- Onionthe original
Fit is the average pairing score against butter, flour, pepper, bread, gruyere cheese, parmesan cheese. 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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